# Menu 4 − Torque and current control

Mode: RFC‑A

RFC-A and RFC-S modes

The diagram below is common to both RFC-A and RFC-S modes.

The drive can have a heavy duty rating intended for applications where high overload current may be required under transient conditions, or it can have a normal duty rating where a lower level of overload current is required, or it can have a no-overload rating. The duty rating is selected automatically by the drive based on the setting of Rated Current (05.007). See Maximum Heavy Duty Rating (11.032) for more details. The different duty ratings modify the motor protection characteristic (see Motor Thermal Time Constant 1 (04.015)), and also change the maximum settings for the current limits. In a drive that contains multiple power modules Full Scale Current Kc (11.061) is the full scale current of an individual module multiplied by the number of modules. Maximum Heavy Duty Rating (11.032) and Maximum Rated Current (11.060) are the value for an individual module multiplied by the number of modules.

RFC-A mode

The torque reference is normally provided by the speed controller, or from the torque reference, or as a combination of both depending on the value of the Torque Mode Selector (04.011). During supply loss or when standard ramp mode is selected and the motor is regenerating it is possible that the torque producing current reference may be provided by the d.c. bus voltage controller as shown above. The torque reference is converted to the torque producing current reference based on the level of motor flux and then current limits are applied. For more details of the current limit system and the calculation of the variable maximums that limit the current limit user parameters (VM_MOTOR1_CURRENT_LIMIT and VM_MOTOR2_CURRENT_LIMIT) see the "Drive Limits" document included in this parameter reference guide.

RFC-S mode

The torque reference is provided by the speed controller, or from the torque reference, or as a combination of both depending on the value of the Torque Mode Selector (04.011). During supply loss or when standard ramp mode is selected and the motor is regenerating it is possible that the torque producing current reference may be provided by the d.c. bus voltage controller as shown above. The torque reference is converted into the final current reference and can include the effect of changes in magnet flux and then the current limits are applied. For more details of the current limit system and the calculation of the variable maximums that limit the current limit user parameters (VM_MOTOR1_CURRENT_LIMIT and VM_MOTOR2_CURRENT_LIMIT) see the "Drive Limits" document included in this parameter reference guide. The final current reference defines the current magnitude that should be applied to the motor which is split into d and q axis components depending on the Rated Torque Angle (05.089). Either the d or q axis current may be further modified to limit the motor voltage when flux weakening is required.

Torque correction systems are provided to adjust the torque reference. The first is based on torque calculated by the drive. This is useful when operating in torque mode to trim the torque produced by the motor to make it more consistent as the speed varies. The other removes selected torque harmonics from the motor torque. This is useful for removing steady state motor torque components caused by the load. These systems are shown in the diagram below.

Parameter | 04.001 Current Magnitude
--- | ---
Short description | Shows the instantaneous drive output current
Mode | RFC‑A
Minimum | −VM_DRIVE_CURRENT_UNIPOLAR | Maximum | VM_DRIVE_CURRENT_UNIPOLAR
Default |  | Units | A
Type | 32 Bit Volatile | Update Rate | 4ms write
Display Format | Standard | Decimal Places | 3
Coding | RO, FI, VM, ND, NC, PT

Instantaneous level of fundamental current at the drive output terminals in r.m.s. amps.

Parameter | 04.002 Torque Producing Current
--- | ---
Short description | Shows the instantaneous level of torque producing current
Mode | RFC‑A
Minimum | −VM_DRIVE_CURRENT | Maximum | VM_DRIVE_CURRENT
Default |  | Units | A
Type | 32 Bit Volatile | Update Rate | 250µs write
Display Format | Standard | Decimal Places | 3
Coding | RO, FI, VM, ND, NC, PT

Iq, Torque Producing Current (04.002) is the instantaneous level of torque producing current scaled so that it represents the r.m.s. level of current under steady state conditions. Iq, Torque Producing Current (04.002) is proportional to the torque produced by the motor provided field weakening is not active. For field weakening operation the Iq, Torque Producing Current (04.002) is boosted for a given level of torque to compensate for the reduction in the motor flux.

Sign of Iq, Torque Producing Current (04.002) | Sign of frequency or speed | Direction of motor torque
+ | + | Accelerating
- | + | Decelerating
+ | - | Decelerating
- | - | Accelerating

Parameter | 04.003 Final Torque Reference
--- | ---
Short description | Shows the final torque reference
Mode | RFC‑A
Minimum | −VM_TORQUE_CURRENT | Maximum | VM_TORQUE_CURRENT
Default |  | Units | %
Type | 16 Bit Volatile | Update Rate | 250µs write
Display Format | Standard | Decimal Places | 1
Coding | RO, FI, VM, ND, NC, PT

The Speed Controller Output (03.004) can include a feed forward torque that will provide the torque necessary to accelerate the load inertia. This can be combined with the Torque Reference (04.008) and the Torque Offset (04.009) as defined by the Torque Mode Selector (04.011) to give the Final Torque Reference (04.003) as a percentage of rated motor torque.

Parameter | 04.004 Final Current Reference
--- | ---
Short description | Shows the final current reference after the current limits
Mode | RFC‑A
Minimum | −VM_TORQUE_CURRENT | Maximum | VM_TORQUE_CURRENT
Default |  | Units | %
Type | 16 Bit Volatile | Update Rate | 4ms write
Display Format | Standard | Decimal Places | 1
Coding | RO, FI, VM, ND, NC, PT

The Final Torque Reference (04.003) is converted into the Final Current Reference (04.004) by applying a torque to current conversion and by applying the Final Current Limit (04.018). The torque to current conversion is applied as follows:

Current reference = Final Torque Reference (04.003) x Motor Rated Flux / Motor Flux

It is possible to disable, or change the method for the flux compensation using Flux Compensation (05.028). This may be required, for example to prevent motor instability when an inaccurate value for Rated Speed (05.008) is being used.

Parameter | 04.005 Motoring Current Limit
--- | ---
Short description | Defines the current limit used when the motor is being accelerated away from standstill
Mode | RFC‑A
Minimum | −VM_MOTOR1_CURRENT_LIMIT | Maximum | VM_MOTOR1_CURRENT_LIMIT
Default | Default RFC_A Current Limit | Units | %
Type | 16 Bit User Save | Update Rate | 4ms read
Display Format | Standard | Decimal Places | 1
Coding | RW, VM

The Motoring Current Limit (04.005) limits the current when the motor is being accelerated away from standstill. The Regenerating Current Limit (04.006) limits the current when the motor is being decelerated towards standstill. If the Symmetrical Current Limit (04.007) is below the Motoring Current Limit (04.005) then it is used instead of the Motoring Current Limit (04.005). If the Symmetrical Current Limit (04.007) is below the Regenerating Current Limit (04.006) then it is used instead of the Regenerating Current Limit (04.006).

The maximum possible current limit (VM_MOTOR1_CURRENT_LIMIT [MAX]) varies between drive sizes with default parameters loaded. For some drive sizes the default value may be reduced below the value given by the parameter range limiting.

Parameter | 04.006 Regenerating Current Limit
--- | ---
Short description | Defines the current limit used when the motor is being decelerated towards standstill
Mode | RFC‑A
Minimum | −VM_MOTOR1_CURRENT_LIMIT | Maximum | VM_MOTOR1_CURRENT_LIMIT
Default | Default RFC_A Current Limit | Units | %
Type | 16 Bit User Save | Update Rate | 4ms read
Display Format | Standard | Decimal Places | 1
Coding | RW, VM

See Motoring Current Limit (04.005).

Parameter | 04.007 Symmetrical Current Limit
--- | ---
Short description | Defines the symmetrical current limit
Mode | RFC‑A
Minimum | −VM_MOTOR1_CURRENT_LIMIT | Maximum | VM_MOTOR1_CURRENT_LIMIT
Default | Default RFC_A Current Limit | Units | %
Type | 16 Bit User Save | Update Rate | 4ms read
Display Format | Standard | Decimal Places | 1
Coding | RW, VM

See Motoring Current Limit (04.005).

Parameter | 04.008 Torque Reference
--- | ---
Short description | Defines the torque reference
Mode | RFC‑A
Minimum | −VM_USER_CURRENT_HIGH_RES | Maximum | VM_USER_CURRENT_HIGH_RES
Default | 0.00 | Units | %
Type | 32 Bit User Save | Update Rate | 250µs read
Display Format | Standard | Decimal Places | 2
Coding | RW, VM

The torque reference is produced as given in the table below. The result is the required torque reference as a percentage of rated motor torque.

Torque Offset Select (04.010) | Torque reference
Offset (-1) | Torque Offset (04.009)
Reference (0) | Torque Reference (04.008)
Ref + Offset (1) | Torque Reference (04.008) + Torque Offset (04.009)

Parameter | 04.009 Torque Offset
--- | ---
Short description | Defines the torque offset that can be added to the torque reference or selected as the torque reference.
Mode | RFC‑A
Minimum | −VM_USER_CURRENT | Maximum | VM_USER_CURRENT
Default | 0.0 | Units | %
Type | 16 Bit User Save | Update Rate | 250µs read
Display Format | Standard | Decimal Places | 1
Coding | RW, VM

See Torque Reference (04.008).

Parameter | 04.010 Torque Offset Select
--- | ---
Short description | Selects the final torque reference as a combination of the torque reference and torque offset.
Mode | RFC‑A
Minimum | -1 | Maximum | 1
Default | 0 | Units |
Type | 8 Bit User Save | Update Rate | 4ms read
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text
-1 | Offset
0 | Reference
1 | Ref + Offset

See Torque Reference (04.008).

Parameter | 04.011 Torque Mode Selector
--- | ---
Short description | Defines the torque mode used by the drive
Mode | RFC‑A
Minimum | 0 | Maximum | 5
Default | 0 | Units |
Type | 8 Bit User Save | Update Rate | 4ms read
Display Format | Standard | Decimal Places | 0
Coding | RW

The value of the Torque Mode Selector (04.011) defines how the Final Torque Reference (04.003) is produced. The inputs to the torque mode selector system are referred to below as the Speed control torque reference and the User torque reference. The Speed control torque reference is the Speed Controller Output (03.004), combined with the Inertia Compensation Torque (02.038) if this is enabled. The User torque reference is the Torque Reference (04.008), combined with the Torque Offset (04.009) if this is enabled. Each of the modes is described below.

Mode 0 and Mode 4 use speed control with the combined output of the ramp system and the hard speed reference as the reference. The other modes are torque control modes (although the speed controller may be active). In these modes the ramp system output is not used, but the output of the ramp system (Post Ramp Reference (02.001)) is constantly preset with Speed Feedback (03.002) − Hard Speed Reference (03.022). This prevents a transient if the mode is changed to 0 or 4 while the drive is active, or the drive run is removed and the motor is stopped under ramp control, i.e. Stop Mode (06.001) is 1 or 2.

0: Speed control mode
The Final Torque Reference (04.003) is the Speed controller torque reference.

1: Torque control
The Final Torque Reference (04.003) is the User torque reference. The speed is not limited by the drive but, the drive will trip at the over-speed threshold if runaway occurs.

2: Torque control with speed override
The drive effectively operates in speed control and Final Torque Reference (04.003) is controlled by the Speed controller torque reference, however this is limited between 0 and the User torque reference. The effect is to produce an operating area as shown below if the Speed controller torque reference and the User torque reference are both positive. The speed controller will attempt to accelerate the motor to the Final Speed Reference (03.001) with a torque equivalent to the User torque reference. However, the speed cannot be forced above the Final Speed Reference (03.001) by the drive because the required torque would be negative, and so it would be clamped to zero.

Depending on the sign of the Final Speed Reference (03.001) and the User torque reference there are four possible areas of operation as shown below.

3: Coiler/uncoiler mode
Positive Final Speed Reference (03.001): Positive User torque reference gives torque control with a positive speed limit defined by the Final Speed Reference (03.001). A negative User torque reference gives torque control with a negative speed limit of -5rpm.

Negative Final Speed Reference (03.001): Negative User torque reference gives torque control with a negative speed limit defined by the Final Speed Reference (03.001). A positive User torque reference gives torque control with a positive speed limit of +5rpm.

Example of coiler operation:
This is an example of a coiler operating in the positive direction. The Final Speed Reference (03.001) is set to a positive value just above the coiler reference speed. If the User torque reference is positive the coiler operates with a limited speed, so that if the material breaks the speed does not exceed a level just above the reference. It is also possible to decelerate the coiler with a negative User torque reference. The coiler will decelerate down to -5rpm until a stop is applied. The operating area is shown below:

Example of uncoiler operation:
This is an example for an uncoiler operating in the positive direction. The Final Speed Reference (03.001) should be set to a level just above the maximum normal speed. When the User torque reference is negative the uncoiler will apply tension and try and rotate at 5rpm in reverse, and so take up any slack. The uncoiler can operate at any positive speed applying tension. If it is necessary to accelerate the uncoiler a positive User torque reference is used. The speed will be limited to the Final Speed Reference (03.001). The operating area is the same as that for the coiler and is shown below:

4: Speed control with torque feed-forward
The Speed control torque reference and User torque reference are summed so that the drive operates under speed control, but a torque value may be added to the output of the speed controller. This can be used to improve the regulation of systems where the speed controller gains need to be low for stability.

5: Bi-directional torque control with speed override
The drive effectively operates in speed control and Final Torque Reference (04.003) is controlled by the Speed controller torque reference. If the User torque reference is positive then the speed reference is Final Speed Reference (03.001) and the torque is limited to the User torque reference. Therefore for any negative speed and any positive speed up to Final Speed Reference (03.001) the motor will produce the required positive torque. If the speed exceeds Final Speed Reference (03.001) no torque will be produced. The system works in the same way for a negative User torque reference, but with a speed limit of -Final Speed Reference (03.001). This system can be used for torque control in either direction with a safe speed limit in either direction if the load torque is less than the applied torque (i.e. the load is removed). The diagram below shows the possible regions of operation.

Parameter | 04.012 Current Reference Filter 1 Time Constant
--- | ---
Short description | Defines the time constant of a first order filter that can be applied to the final current reference
Mode | RFC‑A
Minimum | 0.0 | Maximum | 25.0
Default | 0.0 | Units | ms
Type | 8 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 1
Coding | RW, BU

Current Reference Filter 1 Time Constant (04.012) defines the time constant of a first order filter that can be applied to the Final Current Reference (04.004). The filter is provided to reduce acoustic noise and vibration produced as a result of position feedback quantisation. The filter introduces a lag in the speed controller loop, and so the speed controller gains may need to be reduced to maintain stability as the filter time constant is increased. The time constant used is dependent on Speed Controller Gain Select (03.016) so that different time constants can be used with different gains. Current Reference Filter 1 Time Constant (04.012) is used if Speed Controller Gain Select (03.016) = 0, and Current Reference Filter 2 Time Constant (04.023) is used if Speed Controller Gain Select (03.016) = 1.

If Low-pass Filter Cut-off Frequency (04.050) is set to a value of 10Hz or greater then it overrides the settings of Current Reference Filter 1 Time Constant (04.012) and Current Reference Filter 2 Time Constant (04.023).

Parameter | 04.013 Current Controller Kp Gain
--- | ---
Short description | Defines the current loop controller proportional gain
Mode | RFC‑A
Minimum | 0 | Maximum | 30000
Default | 150 | Units |
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW

Current Controller Kp Gain (04.013) and Current Controller Ki Gain (04.014) are the proportional and integral gains of the current controllers. It is possible to use the current controller in standard mode (Current Controller Mode (04.030) = 0) or high performance mode (Current Controller Mode (04.030) = 1). The set up method for the current controller gains is described separately for each of these modes below. It should be noted that when an auto-tune is performed that measures the Transient Inductance (05.024) and Stator Resistance (05.017) the Current Controller Kp Gain (04.013) and Current Controller Ki Gain (04.014) are automatically set to the levels defined in the description for standard mode even if high performance mode is selected. These gains will give good performance in standard mode and produce moderate acoustic noise due to position feedback quantisation with a standard incremental encoder. These represent the maximum levels that are likely to be used with this mode in most applications. For high performance mode it is recommended that a high resolution position feedback device is used or else the acoustic noise due to position feedback quantisation is likely to be excessive. In high performance mode the proportional gain can be increased to a higher level as given in the description of this mode.

Standard mode
Standard mode can be used to give good current control dynamic performance and is compatible with the performance of Unidrive SP. The current controller gains can either be set using auto-tuning (see Auto-tune (05.012)) or the values can be set up manually by the user. The calculations given below are those used by the auto-tuning system and should give good performance without excessive overshoot.

The proportional gain, Current Controller Kp Gain (04.013), is the most critical value in controlling the performance of the current controllers. The required value can be calculated as

Current Controller Kp Gain (04.013) = (L / T) x (Ifs / Vfs) x (256 / 5)

where:

T is the sample time of the current controllers. The drive compensates for any change of sample time, and so it should be assumed that the sample time is equivalent to the base value of 167μs.

L is the motor inductance. For a servo motor this is half the phase to phase inductance that is normally specified by the manufacturer. For an induction motor this is the per phase transient inductance (σLs). The inductance for either of these motors can be taken from the manufacturers data or it can be obtained from the value stored in the Transient Inductance (05.024) after auto-tuning.

Ifs is the peak full scale current feedback, i.e. full scale current x √2. The r.m.s. full scale current is given by Full Scale Current Kc (11.061), and so Ifs = Full Scale Current Kc (11.061) x √2.

Vfs is the maximum d.c. bus voltage.

Therefore:

Current Controller Kp Gain (04.013) = (L / 167μs) x (Kc x √2/ Vfs) x (256 / 5) = K x L x Kc

Where K = [√2 / (Vfs x 167μs)] x (256 / 5)

There is one value of the scaling factor K for each drive voltage rating as shown in the table below.

Drive Rated Voltage (11.033) | Vfs | K
200V | 415V | 1045
400V | 830V | 522
575V | 990V | 438
690V | 1190V | 364

The integral gain, Current Controller Ki Gain (04.014), is less critical. A suggested value which matches the zero with the pole caused by the electrical time constant of the motor and ensures that the integral term does not contribute to current overshoot is given by

Current Controller Ki Gain (04.014) = Current Controller Kp Gain (04.013) x 256 x T / τm

Where τm is the motor time constant (L / R). R is the per phase stator resistance of the motor (i.e. half the resistance measured between two phases).

Therefore:

Current Controller Ki Gain (04.014) = (K x L x Kc) x 256 x 167μs x R / L = 0.0427 x K x R x Kc

The above equations give the gain values that should give a good response with minimal overshoot. If required the gains can be adjusted to modify the performance as follows:

1. Current Controller Ki Gain (04.014) can be increased to improve the performance of the current controllers by reducing the effects of inverter non-linearity. These effects become more significant with higher switching frequency. These effects will be more significant for drives with higher current ratings and higher voltage ratings. If Current Controller Ki Gain (04.014) is increased by a factor of 4 it is possible to get up to 10% overshoot in response to a step change of current reference. For high performance applications, it is recommended that Current Controller Ki Gain (04.014) is increased by a factor of 4 from the auto-tuned values. As the inverter non-linearity is worse with higher switching frequencies it is may be necessary to increase Current Controller Ki Gain (04.014) by a factor of 8 for operation with 16kHz switching frequency.
2. It is possible to increase Current Controller Kp Gain (04.013) to reduce the response time of the current controllers. If Current Controller Kp Gain (04.013) is increased by a factor of 1.5 then the response to a step change of reference will give 12.5% overshoot. It is recommended that Current Controller Ki Gain (04.014) is increased in preference to Current Controller Kp Gain (04.013).

As already stated, the drive compensates for changes of switching frequency and the sampling method used by the controller. The table below shows the adjustment applied to the proportional and integral gains.

Switching Frequency (05.037) | Current controller sample time Current | Current Controller Kp Gain (04.013) adjustment | Current Controller Ki Gain (04.014) adjustment
2kHz | 250μs | x 167 / 250 = 0.7 | x 1.0
3kHz | 167μs | x 167 / 167 = 1.0 | x 1.0
4kHz | 125μs | x 167 / 125 = 1.3 | x 1.0
6kHz | 83μs | x 167 / 83 = 2.0 | x 1.0
8kHz | 62.5μs | x 167 / 62.5 = 2.7 | x 1.0
12kHz | 83μs | x (167 / 83) x (4 / 3) = 2.7 | x 4 / 3 = 1.3
16kHz | 62.5μs | x (167 / 62.5) x (4 / 3) = 3.6 | x 4 / 3 = 1.3

The amount of acoustic noise produced in the motor from position feedback quantisation is related to the resolution of the position feedback and the product of the speed controller and current controller proportional gains. The values in this table can be used in conjunction with the speed controller loop proportional gain to assess the amount of acoustic noise that is likely to be produced.

High performance mode
High performance mode gives fast closed-loop dynamic performance as though the proportional gain has been set to the maximum value defined below. This is the maximum value that should be used to prevent excessive over-shoot or instability. It should be noted that this is 5 times the maximum value used for standard mode.

Current Controller Kp Gain (04.013) = (L / T) x (Ifs / Vfs) x 256 = K x L x Kc x 5

The closed-loop dynamic performance defines the response of the current controllers to a change of current reference. This response cannot be changed by modifying Current Controller Kp Gain (04.013), however the ability of the current controllers to reject voltage disturbances is affected by Current Controller Kp Gain (04.013). Normally the auto-tuned value (which is one fifth of the maximum recommended value) will give good rejection of voltage disturbances, but the proportional gain can be increased up to the maximum value to improve this. It should be noted that the higher closed-loop response of the controllers means that encoder position quantisation will cause significant acoustic noise in the motor unless a high resolution encoder is used. Increasing Current Controller Kp Gain (04.013) also increases acoustic noise due to noise on the current feedback. High performance mode uses the measured motor resistance and inductance, and so it is recommended that these are obtained with auto-tuning using test 1 or 2.

The integral gain provides a trim on the currents, and generally the auto-tuned value should be sufficient, however, this may be increased if required.

The drive compensates for changes of switching frequency used by the controller. The table below shows the adjustment applied to the proportional and integral gains.

Switching Frequency (05.037) | Current controller sample time Current | Current Controller Kp Gain (04.013) adjustment | Current Controller Ki Gain (04.014) adjustment
2kHz | 500us | x 167 / 500 = 0.3 | x 1.0
3kHz | 333us | x 167 / 333 = 0.5 | x 1.0
4kHz | 250us | x 167 / 250 = 0.7 | x 1.0
6kHz | 167μs | x 167 / 167 = 1.0 | x 1.0
8kHz | 125μs | x 167 / 125 = 1.3 | x 1.0
12kHz | 83μs | x 167 / 83 = 2.0 | x 1.0
16kHz | 62.5μs | x 167 / 62.5 = 2.7 | x 1.0

Parameter | 04.014 Current Controller Ki Gain
--- | ---
Short description | Defines the current loop controller integral gain
Mode | RFC‑A
Minimum | 0 | Maximum | 30000
Default | 2000 | Units |
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW

See Current Controller Kp Gain (04.013).

Parameter | 04.015 Motor Thermal Time Constant 1
--- | ---
Short description | Set to the thermal time constant for the motor
Mode | RFC‑A
Minimum | 1.0 | Maximum | 3000.0
Default | 89.0 | Units | s
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 1
Coding | RW

A dual time constant thermal model is provided that can be used to estimate the motor temperature as a percentage of its maximum allowed temperature. The input to the model is the Current Magnitude (04.001). Throughout the following discussion Rated Current (05.007) is used in the model assuming Select Motor 2 Parameters (11.045) = 0. If Select Motor 2 Parameters (11.045) = 1 then M2 Rated Current (21.007) is used instead. It should be noted that if the parameters that have been added in addition to those in Unidrive SP are left at their default values the model is a simple single time constant model as provided in Unidrive SP.

Percentage Losses
The losses in the motor are calculated as a percentage value.

Percentage Losses = 100% x [Load Related Losses + Iron Losses]

where:
Load Related Losses = (1 - Kfe) x (I / (K1 x IRated))2
Iron Losses = Kfe x (w / wRated)1.6

where:
I = Current Magnitude (04.001)
IRated = Rated Current (05.007)
Kfe = Rated Iron Losses As Percentage Of Losses (04.039) / 100%

The iron losses are relatively low in motors that have a rated frequency of 60Hz or less, and so the motor could be modelled based on load related losses alone. This can be done by setting Kfe to zero. In motors where iron losses are significant, Kfe defines the proportion of losses that are iron losses under rated conditions (i.e. rated current and rated frequency). For example if the iron losses are 30% of losses and other losses are 70% of losses under rated conditions Rated Iron Losses As Percentage Of Losses (04.039) should be set to 30%.

The value of K1 defines the continuous allowable motor overload as a proportion of the Rated Current (05.007) before the Motor Protection Accumulator (04.019) reaches 100%. The value of K1 can be used to model reduced cooling at low speeds and to allow the motor to operate under rated conditions with a small margin to prevent spurious trips. K1 is defined in more detail later.

Motor Protection Accumulator
So far the steady state motor losses have been defined, but the motor model must estimate the temperature within the motor under dynamically changing conditions, and so the Motor Protection Accumulator (04.019) is given by the following equation.

T = Percentage Losses x [(1 − K2) (1 − e-t/τ1) + K2 (1 − e-t/τ2)]

where
T = Motor Protection Accumulator (04.019)
K2 = Motor Thermal Time Constant 2 Scaling (04.038) / 100%
τ1 = Motor Thermal Time Constant 1 (04.015)
τ2 = Motor Thermal Time Constant 2 (04.037)

[(1 − K2) (1 − e-t/τ1) + K2 (1 − e-t/τ2)] gives the effects of the thermal time constants in the motor. K2 defines the ratio of the contribution to the Motor Protection Accumulator (04.019) value from each of the time constants. If K2 is set to its default value of 0 then only Motor Thermal Time Constant 1 (04.015) is included and the model will give the temperature of the main mass of the motor body. To give better protection to the motor, the model can be used to model a particular point in the motor, for example the stator windings. This can be done by including an additional shorter time constant representing the thermal impedance between the windings and the main mass of the motor body which can be modelled with Motor Thermal Time Constant 2 (04.037).

Reduced cooling with lower speed
If Rated Current (05.007) ≤ Maximum Heavy Duty Rating (11.032) then K1 is defined as shown below. If Low Speed Thermal Protection Mode (04.025) = 0 the characteristic is intended for a motor which can operate at rated current over the whole speed range. Induction motors with this type of characteristic normally have forced cooling. If Low Speed Thermal Protection Mode (04.025) = 1 the characteristic is intended for motors where the cooling effect of motor fan reduces with reduced motor speed below half of rated speed. The maximum value for K1 is 1.05, so that above the knee of the characteristics the motor can operate continuously up to 105% of rated current.

If Rated Current (05.007) > Maximum Heavy Duty Rating (11.032) then K1 is defined as shown below. Two different characteristics are provided, but in both cases the motor performance is limited at lower speeds and the permissible overload is reduced from 105% to 101%.

Time for Motor Protection Accumulator to reach 100%
Assuming a single time constant model is being used (i.e. Motor Thermal Time Constant 2 Scaling (04.038), the time for the Motor Protection Accumulator (04.019) to change from its initial value to 100% is given by the following equation:

Time to reach 100.0% = -τ1 x ln[(1 − C1) / (C0 − C1)]

C0 represents the conditions that have persisted for long enough for the Motor Protection Accumulator (04.019) to reach a steady state value. If the motor current and speed are I0 and w0 then,

C0 = [(1 - Kfe) x (I0 / (K1 x IRated))2] + [Kfe x (w0 / wRated)1.6]

C1 represents the conditions that begin at the start of the time being calculated. If the motor current and speed are by I1 and w1 then,

C1 = [(1 - Kfe) x (I1 / (K1 x IRated))2] + [Kfe x (w1 / wRated)1.6]

Example 1: The effect of iron losses are not modelled (Kfe = 0), Motor Thermal Time Constant 1 (04.015) = 89s, the initial current is zero, Rated Current (05.007) ≤ Maximum Heavy Duty Rating (11.032) and the new level of current is 1.5 x Rated Current (05.007).

C0 = 0
C1 = [1.5 / (1.05 x 1.0)]2 = 2.041

Time to reach 100.0% = -89 x ln(1 − 1/C1) = -89 x ln(1 − 1/2.041) = 60s

This is the default setting for Open-loop and RFC-A modes allowing an induction motor to run at 150% rated current for 60s from cold.

Example 2: The effect of iron losses are not modelled (Kfe = 0), Motor Thermal Time Constant 1 (04.015) = 89s, the initial current is Rated Current (05.007), Rated Current (05.007) ≤ Maximum Heavy Duty Rating (11.032) and the new level of current is 1.5 x Rated Current (05.007).

C0 = [1.0 / (1.05 x 1.0)]2 = 0.907
C1 = [1.5 / (1.05 x 1.0)]2 = 2.041

Time to reach 100.0% = -89 x ln((1 − C1) / (C0 − C1)) = -89 x ln[(1 − 2.041) / (0.907 − 2.041)] = 7.6s

This is the default setting for Open-loop and RFC-A modes allowing an induction motor to run at 150% rated current for 7.6s after running under rated conditions for a significant period of time.

Motor Protection Accumulator Reset
The initial value in the Motor Protection Accumulator (04.019) at power-up is defined by Motor Protection Accumulator Power-up Value (04.036) as given in the table below.

Motor Protection Accumulator Power-up Value (04.036) | Motor Protection Accumulator (04.019) at power-up
Power Down | The value is saved at power-down and is used as the initial value at power-up.
Zero | The value is set to zero
Real Time | If a real-time clock is present and if Date/Time Selector (06.019) is set up to select the real-time clock then the value saved at power-down is modified to include the effect of the motor thermal protection time constants over the time between power-down and power-up. This modified value is then used as the initial value at power-up. If no real time clock is present then and this option is selected then the value saved at power-down is used as the initial value.

The Motor Protection Accumulator (04.019) is reset under the following conditions:

1. Motor Thermal Time Constant 1 (04.015) is set to 0.0. Note that this is not possible in the standard product as the minimum parameter value is 1.0.
2. Select Motor 2 Parameters (11.045) is modified.
3. Rated Current (05.007) is modified when Select Motor 2 Parameters (11.045) = 0, or M2 Rated Current (21.007) is modified when Select Motor 2 Parameters (11.045) = 1.
4. Thermal Protection Mode (04.016) is modified.

Motor Protection Accumulator Warning
If Percentage Losses > 100% then eventually the Motor Protection Accumulator (04.019) will reach 100% causing the drive to trip or the current limits to be reduced. If this is the case and Motor Protection Accumulator (04.019) > 70.0% then [Motor Overload] alarm indication is given and Motor Overload Alarm (10.017) is set to one.

Parameter | 04.016 Thermal Protection Mode
--- | ---
Short description | Set to the require thermal protection mode
Mode | RFC‑A
Minimum | 0 | Maximum | 4
Default | 0 | Units |
Type | 8 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text
0 | Motor Trip
1 | Motor Limit
2 | Drive Limit
3 | Both Limit
4 | Disabled

Thermal Protection Mode (04.016) defines the action taken by the drive when Motor Protection Accumulator (04.019) reaches 100% and/or Percentage Of Drive Thermal Trip Level (07.036) exceeds 90%. The actions for each mode are given in the table below.

Thermal Protection Mode (04.016) | Actions
Motor Trip (0) | Motor Too Hot trip is initiated when Motor Protection Accumulator (04.019) reaches 100%. No current limiting. Motor Protection Accumulator (04.019) is limited to 100.0%.
Motor Current Limit (1) | Motor Too Hot trip is disabled. Current limiting on motor overload as described below. Motor Protection Accumulator (04.019) is limited to 100.0%.
Drive Current Limit (2) | Motor Too Hot trip is initiated when Motor Protection Accumulator (04.019) reaches 100%. Current limiting on drive thermal monitoring as described below. Motor Protection Accumulator (04.019) is limited to 100.0%.
Motor and Drive Current Limit (3) | Motor Too Hot trip is disabled. Current limiting on motor overload and drive thermal monitoring as described below. Motor Protection Accumulator (04.019) is limited to 100.0%.
Disabled (4) | Motor Too Hot trip is disabled and Motor Overload alarm is disabled. No current limiting. Motor Protection Accumulator (04.019) is limited to 200.0%.

The current limit is derived from the current limit parameters (i.e. Motoring Current Limit (04.005), etc.) depending on the set-up and conditions. The current limit can be further limited by current limit on motor overload and/or drive temperature monitoring as shown below to give the Final Current Limit (04.018).

Current limiting on motor overload
When the Motor Protection Accumulator (04.019) reaches 100.0% the current limit is limited to (K1 – 0.05) x 100.0%. This limitation is removed when the Motor Protection Accumulator (04.019) falls below 95.0%. (K1 is defined in the description of Motor Thermal Time Constant 1 (04.015).)

Drive thermal monitoring current limiting
If Percentage Of Drive Thermal Trip Level (07.036) exceeds 90% the current limit is modified as follows:

Final Current Limit (04.018) = Current limit x (100% - Percentage Of Drive Thermal Trip Level (07.036)) / 10%

If both of the above attempt to reduce the final current limit the lowest calculated value of current limit is used.

This system has the effect of reducing the current limit to zero at the point where the drive should be tripped because its thermal monitoring has reached a trip threshold. This is intended to limit the load on the drive to prevent it from tripping when supplying a load that increases with speed and does not include rapid transients.

Parameter | 04.017 Magnetising Current
--- | ---
Short description | Shows the instantaneous level of magnetising current
Mode | RFC‑A
Minimum | −VM_DRIVE_CURRENT | Maximum | VM_DRIVE_CURRENT
Default |  | Units | A
Type | 32 Bit Volatile | Update Rate | 250µs write
Display Format | Standard | Decimal Places | 3
Coding | RO, FI, VM, ND, NC, PT

Id, Magnetising Current (04.017) is the instantaneous level of magnetising current scaled so that it represents the r.m.s. level of magnetising current under steady state conditions.

Parameter | 04.018 Final Current Limit
--- | ---
Short description | Shows the final current limit that is applied to the torque producing current
Mode | RFC‑A
Minimum | −VM_TORQUE_CURRENT | Maximum | VM_TORQUE_CURRENT
Default |  | Units | %
Type | 16 Bit Volatile | Update Rate | 4ms write
Display Format | Standard | Decimal Places | 1
Coding | RO, VM, ND, NC, PT

Final Current Limit (04.018) is the current limit level that is applied to give the Final Current Reference (04.004).

Parameter | 04.019 Motor Protection Accumulator
--- | ---
Short description | Shows the level of the motor protection accumulator
Mode | RFC‑A
Minimum | 0.0 | Maximum | 200.0
Default |  | Units | %
Type | 16 Bit Power Down Save | Update Rate | Background write
Display Format | Standard | Decimal Places | 1
Coding | RO, ND, NC, PT

See Motor Thermal Time Constant 1 (04.015).

Parameter | 04.020 Percentage Load
--- | ---
Short description | Shows the level of torque producing current as a percentage of rated torque producing current for the motor
Mode | RFC‑A
Minimum | −VM_USER_CURRENT | Maximum | VM_USER_CURRENT
Default |  | Units | %
Type | 16 Bit Volatile | Update Rate | Background write
Display Format | Standard | Decimal Places | 1
Coding | RO, FI, VM, ND, NC, PT

Percentage Load (04.020) gives the Iq, Torque Producing Current (04.002) as a percentage of the rated torque producing current for the motor.

Sign of Percentage Load (04.020) | Sign of frequency or speed | Direction of motor torque
+ | + | Accelerating
- | + | Decelerating
+ | - | Decelerating
- | - | Accelerating

With synchronous reluctance or high saliency permenant motors it is difficult to predict the torque based on the motor current because the torque depends on the motor inductance which varies with current. To obtain an indication of torque (motor load) the rated motor torque should be set in Rated Torque (04.041) and Percentage Torque (04.026) should be used to give the torque or load indication.

Parameter | 04.021 Current Feedback Filter Disable
--- | ---
Short description | Disables the 4ms filter applied to current feedback parameters.
Mode | RFC‑A
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 1 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW

If Current Feedback Filter Disable (04.021) = 0 a 4ms filter is applied to the current feedback components measured by the drive to be used in Iq, Torque Producing Current (04.002) and Id, Magnetising Current (04.017). This filter removes ripple components associated with the PWM switching. If Current Feedback Filter Disable (04.021) = 1, the filter is disabled and the user parameters are based on the current components sampled every 250us.

Parameter | 04.022 Inertia Compensation Enable
--- | ---
Short description | Set to enable inertia compensation
Mode | RFC‑A
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 1 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW

If Inertia Compensation Enable (04.022) is set to one the Inertia Compensation Torque (02.038) is added to the output of the speed controller. The Inertia Compensation Torque (02.038) is calculated based on a value of load inertia supplied by the user (Motor And Load Inertia (03.018)) and the rate of change of the speed reference. This can be used in speed or torque controller applications to provide the torque necessary to accelerate or decelerate the load.

Parameter | 04.023 Current Reference Filter 2 Time Constant
--- | ---
Short description | Defines the time constant of an alternative first order filter that can be applied to the final current reference
Mode | RFC‑A
Minimum | 0.0 | Maximum | 25.0
Default | 0.0 | Units | ms
Type | 8 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 1
Coding | RW, BU

See Current Reference Filter 1 Time Constant (04.012).

Parameter | 04.024 User Current Maximum Scaling
--- | ---
Short description | Defines the maximum for the torque reference and percentage load parameters
Mode | RFC‑A
Minimum | −VM_TORQUE_CURRENT_UNIPOLAR | Maximum | VM_TORQUE_CURRENT_UNIPOLAR
Default | 300.0 | Units | %
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 1
Coding | RW, VM

User Current Maximum Scaling (04.024) defines the variable maximum/minimums VM_USER_CURRENT and VM_USER_CURRENT_HIGH_RES which are applied to Percentage Load (04.020), Torque Reference (04.008) and Torque Offset (04.009). This is useful when routing these parameters to an analog output or when using them as the destination for an analog input, as it allows the full scale value to be defined by the user.

The maximum value (VM_TORQUE_CURRENT_UNIPOLAR [MAX]) varies between drive sizes with default parameters loaded. For some drive sizes the default value may be reduced below the value given by the parameter range limiting.

Parameter | 04.025 Low Speed Thermal Protection Mode
--- | ---
Short description | Set to enable low speed thermal protection mode
Mode | RFC‑A
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 8 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW

See Motor Thermal Time Constant 1 (04.015).

Parameter | 04.026 Percentage Torque
--- | ---
Short description | Calculated torque as a percentage of rated torque
Mode | RFC‑A
Minimum | −VM_USER_CURRENT | Maximum | VM_USER_CURRENT
Default |  | Units | %
Type | 16 Bit Volatile | Update Rate | 4ms write
Display Format | Standard | Decimal Places | 1
Coding | RO, FI, VM, ND, NC, PT

This parameter gives the motor torque with reasonable accuracy as a percentage of rated torque and is intended to be used to trim the torque reference to improve the relationship between the torque reference and the actual motor torque in RFC-A and RFC-S modes. It can also be used as an indication of the motor torque as a percentage of rated torque. The table below shows the parameters that are needed for Percentage Torque (04.026) to operate.

Parameter | Comments
Rated Torque (04.041) | Must be set up so the measured torque can be converted to a percentage.
Stator Resistance (05.017) | Required. Measured during auto-tuning.
Number Of Motor Poles (05.011) | Required.
No-load Core Loss (04.045) | Improves the measured torque accuracy. Measured during auto-tuning in RFC-A mode. Could be estimated during calibration tests with a torque transducer.
Rated Core Loss (04.046) | Further improves the measured torque accuracy. Could be estimated during calibration tests with a torque transducer.
Torque Estimation Minimum Frequency (04.042) | The default value of 5% of rated frequency should be suitable in most applications.
Torque Correction Time Constant (04.043) | Torque trimming is enabled if this is set to a non-zero value. (RFC-A and RFC-S modes only.)
Torque Correction Maximum (04.044) | The default value of 20% is suitable for most applications. (RFC-A and RFC-S modes only.)

The shaft torque of the motor is estimated by the drive and Percentage Torque (04.026) gives this torque as a percentage of the expected Rated Torque (04.041). The default value for Rated Torque (04.041) is zero which disables this feature so that Percentage Torque (04.026) is always zero. To enable this torque estimation system Rated Torque (04.041) should be set to the expected torque from the motor under rated conditions. The percentage torque is calculated as follows.

Torque(%) = [(Output power - Stator losses) / (2π x Output frequency / Motor poles/2)] ×100% / Rated Torque (04.041)
= [(Output Power (05.003) - Stator losses) / (2π x Output frequency / (Number Of Motor Poles (05.011)/2))] ×100% / Rated Torque (04.041)

The stator losses are split into resistance loss and core loss.

Stator losses = Resistance loss + Core power loss

Resistance loss = Current Magnitude (04.001)2 × Temperature Compensated Stator Resistance (05.050)

Core power loss = No-load Core Loss (04.045) + (Rated Core Loss (04.046) - No-load Core Loss (04.045)) x (Torque Producing Current / Rated Torque Producing Current)

If Rated Core Loss (04.046) ≤ No-load Core Loss (04.045) then only the no load value is used and Core power loss = No-load Core Loss (04.045). This provides some compensation for core losses, but not the load dependent component. The core loss power values can be difficult to obtain except by experimental measurement because the loss mechanisms within the motor are complex and are affected by the PWM frequencies applied to the motor by the drive. It is possible to obtain an estimate for No-load Core Loss (04.045) during auto-tuning for RFC-A mode, but not RFC-S mode. As the auto-tuning algorithm cannot measure Rated Core Loss (04.046) this is set to zero, so that it is not used. If power dependent core losses are to be included Rated Core Loss (04.046) must be set by the user.

At low output frequencies this estimate of torque is inaccurate. Torque Estimation Minimum Frequency (04.042) defines the frequency as a percentage of rated frequency where the calculated torque is too inaccurate to use.

For Open-loop and RFC-A modes: FThreshold = Rated Frequency (05.006) x Torque Estimation Minimum Frequency (04.042) / 100.

For RFC-S mode: FThreshold = Rated Speed (05.008) x number of motor poles / 120 x Torque Estimation Minimum Frequency (04.042) / 100.

The table below shows how Percentage Torque (04.026) is calculated at different frequencies.

Condition | Percentage Torque (04.026) RFC-A and RFC-S modes | Percentage Torque (04.026) Open-loop mode
|Output Frequency (05.001)| < FThreshold | Final Torque Reference (04.003)* | 0
FThreshold ≤ |Output Frequency (05.001)| < 2FThreshold | Changes linearly between Final Torque Reference (04.003) and calculated torque including core losses | 0
|Output Frequency (05.001)| ≥ 2FThreshold | Calculated torque including core losses | Calculated torque including core losses

*As the torque reference and actual torque may not align well with some motors, the ratio of the torque reference and measured torque is stored when the frequency is above 2FThreshold and this is then used when the frequency is below 2FThreshold to try and improve the estimated torque.

In RFC-A and RFC-S modes Percentage Torque (04.026) can be used to trim the torque reference and improve the relationship between the torque reference and the actual torque if Torque Correction Time Constant (04.043) is non-zero.

Parameter | 04.030 Current Controller Mode
--- | ---
Short description | Set to enable high performance current controller mode
Mode | RFC‑A
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 1 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW

See Current Controller Kp Gain (04.013).

Parameter | 04.031 Notch Filter Centre Frequency
--- | ---
Short description | Defines the centre frequency for a notch filter to cancel a mechanical resonance
Mode | RFC‑A
Minimum | 50 | Maximum | 1200
Default | 100 | Units | Hz
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW

A notch filter can be inserted be applied to the Final Current Reference (04.004) to remove the effect of a mechanical resonance in the system. Notch Filter Centre Frequency (04.031) defines the centre frequency (f0) in Hertz and Notch Filter Bandwidth (04.032) defines the bandwidth (fBW) which is the frequency difference between the 3dB points of the notch filter in Hertz. The Q of the filter is given by Q = f0 / fBW. If Notch Filter Bandwidth (04.032) is at its default value of zero then the notch filter is disabled. It should be noted that although it is possible to set a bandwidth that is higher than twice the centre frequency, the bandwidth of the filter is limited to twice the centre frequency.

Parameter | 04.032 Notch Filter Bandwidth
--- | ---
Short description | Defines the bandwidth for a notch filter to cancel mechanical resonance
Mode | RFC‑A
Minimum | 0 | Maximum | 1200
Default | 0 | Units | Hz
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW

See Notch Filter Centre Frequency (04.031).

Parameter | 04.033 Inertia Times 1000
--- | ---
Short description | Inertia is in 1000kgm2 units
Mode | RFC‑A
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 1 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW

The inertia in Motor And Load Inertia (03.018) is in kgm2 if this parameter is zero, otherwise if it is one the inertia is in 1000kgm2 units.

Parameter | 04.034 Negative Phase Sequence Current Gain
--- | ---
Short description | Negative Phase Sequence Current Gain
Mode | RFC‑A
Minimum | 0.00 | Maximum | 1.00
Default | 0.00 | Units |
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 2
Coding | RW

Imbalance in the magnetics of the motor can cause imbalance in the drive output currents particularly at higher output frequencies. If this is a problem, then this parameter should be set to 1.00 so that the current controllers attempt to remove the imbalance. This parameter defines the integral gain of the controller used as a proportion of the integral gain being used for the current controllers, and so a lower gain can be selected to remove the current imbalance if required. This feature is only provided if the standard current control mode is used (i.e. Current Controller Mode (04.030) = 0).

Parameter | 04.036 Motor Protection Accumulator Power-up Value
--- | ---
Short description | Defines the initial power-up value of the motor protection accumulator
Mode | RFC‑A
Minimum | 0 | Maximum | 2
Default | 0 | Units |
Type | 8 Bit User Save | Update Rate | Background write
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text
0 | Power down
1 | Zero
2 | Real time

See Motor Thermal Time Constant 1 (04.015).

Parameter | 04.037 Motor Thermal Time Constant 2
--- | ---
Short description | Can be used to define an additional motor thermal time constant
Mode | RFC‑A
Minimum | 1.0 | Maximum | 3000.0
Default | 89.0 | Units | s
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 1
Coding | RW

See Motor Thermal Time Constant 1 (04.015).

Parameter | 04.038 Motor Thermal Time Constant 2 Scaling
--- | ---
Short description | Defines the ratio of the contribution to the motor protection accumulator value from each of the time constants
Mode | RFC‑A
Minimum | 0 | Maximum | 100
Default | 0 | Units | %
Type | 8 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW

See Motor Thermal Time Constant 1 (04.015).

Parameter | 04.039 Rated Iron Losses As Percentage Of Losses
--- | ---
Short description | Set to the rated iron losses of the motor as a percentage of the total losses for the motor
Mode | RFC‑A
Minimum | 0 | Maximum | 100
Default | 0 | Units | %
Type | 8 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW

See Motor Thermal Time Constant 1 (04.015).

Parameter | 04.041 Rated Torque
--- | ---
Short description | Rated motor torque used to calculate percentage torque.
Mode | RFC‑A
Minimum | 0.00 | Maximum | 50000.00
Default | 0.00 | Units | Nm
Type | 32 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 2
Coding | RW

See Percentage Torque (04.026).

Parameter | 04.042 Torque Estimation Minimum Frequency
--- | ---
Short description | Minimum frequency used by the torque correction system
Mode | RFC‑A
Minimum | 0 | Maximum | 100
Default | 5 | Units | %
Type | 8 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW

See Percentage Torque (04.026).

Parameter | 04.043 Torque Correction Time Constant
--- | ---
Short description | Time constant used by the torque correction system
Mode | RFC‑A
Minimum | 0.00 | Maximum | 10.00
Default | 0.00 | Units | s
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 2
Coding | RW

The torque correction system uses the difference between Final Torque Reference (04.003) and Percentage Torque (04.026) to calculate the error between the required and actual torque. This error is used by the torque correction system to apply a trim to the torque reference being used by the drive. If Torque Correction Time Constant (04.043) is set to a non-zero value this system is enabled and Torque Correction Time Constant (04.043) defines the time constant of the correction system. The maximum positive or negative trim that can be applied is defined by Torque Correction Maximum (04.044).

Parameter | 04.044 Torque Correction Maximum
--- | ---
Short description | Maximum trim that can be applied to the torque reference to correct the torque.
Mode | RFC‑A
Minimum | 0 | Maximum | 100
Default | 20 | Units | %
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW

See Torque Correction Time Constant (04.043).

Parameter | 04.045 No-load Core Loss
--- | ---
Short description | Defines the no-load core loss for the motor used by the torque correction system
Mode | RFC‑A
Minimum | 0.000 | Maximum | 99999.999
Default | 0.000 | Units | kW
Type | 32 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 3
Coding | RW

See Percentage Torque (04.026).

Parameter | 04.046 Rated Core Loss
--- | ---
Short description | Defines the rated core loss for the motor used by the torque correction system
Mode | RFC‑A
Minimum | 0.000 | Maximum | 99999.999
Default | 0.000 | Units | kW
Type | 32 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 3
Coding | RW

See Percentage Torque (04.026).

Parameter | 04.049 Magnetising Current Limit
--- | ---
Short description | Magnetising Current Limit
Mode | RFC‑A
Minimum | 0.0 | Maximum | 100.0
Default | 100.0 | Units | %
Type | 16 Bit User Save | Update Rate | Background
Display Format | Standard | Decimal Places | 1
Coding | RW

Magnetising Current Limit (04.049) defines the maximum level of magnetising current used as a percentage of Rated Current (05.007). The magnetising current is normally at the rated level for the motor, but may increase up to this limit when the drive is enabled to raise the flux in the motor as fast as possible. The magnetising current can also be increased above the rated level when the motor is decelerated rapidly from the flux weakening range. The default value for Magnetising Current Limit (04.049) is normally suitable, but may be decreased if required. The maximum level of magnetising current will not be decreased below the rated level for the motor how ever low the value in Magnetising Current Limit (04.049).

Parameter | 04.050 Low-pass Filter Cut-off Frequency
--- | ---
Short description | Overrides the other setting for the current reference low-pass filter and defines the cut-off frequency.
Mode | RFC‑A
Minimum | 0 | Maximum | 1000
Default | 0 | Units | Hz
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW

The current reference low-pass filter is normally set up using its time constant with Current Reference Filter 1 Time Constant (04.012), Current Reference Filter 2 Time Constant (04.023) or M2 Current Reference Filter Time Constant 1 (21.032). If these parameter are used the resolution of the cut-off frequency is poor with shorter time constants. If Low-pass Filter Cut-off Frequency (04.050) is less than 10Hz it has no effect. If it is set to 10Hz or above it overrides all other setting parameters and defines the cut-off frequency in Hz.

Parameter | 04.051 Bi-quad Filter1: a0
--- | ---
Short description | Used to define the a0 coefficient for a bi-quad filter to replace the low-pass filter
Mode | RFC‑A
Minimum | -2.0000 | Maximum | 2.0000
Default | 0.0000 | Units |
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 4
Coding | RW

It is possible to replace low-pass filter defined by Current Reference Filter 1 Time Constant (04.012), Current Reference Filter 2 Time Constant (04.023), M2 Current Reference Filter Time Constant 1 (21.032) or Low-pass Filter Cut-off Frequency (04.050) with a user defined first or second order filter. The replacement filter is a bi-quad filter with the following transfer function.

F(s) = (As2 + Bs + C) / (Ds2 + Es + F)

The coefficients of the transfer function must be translated into the coefficients for the difference equation below which implements this filter with a sample time of 250us.

ON = a0.IN + a1.IN-1 + a2.IN-2 - b1.ON-1 - b2.ON-2

where
Bi-quad Filter1: a0 (04.051) = a0
Bi-quad Filter1: a1 (04.052) = a1
Bi-quad Filter1: a2 (04.053) = a2
Bi-quad Filter1: b1 (04.054) = b1
Bi-quad Filter1: b2 (04.055) = b2

If any of these parameters are changed from their default value of zero then the internal low-pass filter is disabled and the coefficients in these parameters are used to define the replacement filter. A method that can be used to calculate the coefficients, with some examples, is given in the "Digital Filter Design" document included in this parameter reference guide.

Parameter | 04.052 Bi-quad Filter1: a1
--- | ---
Short description | Used to define the a1 coefficient for a bi-quad filter to replace the low-pass filter
Mode | RFC‑A
Minimum | -2.0000 | Maximum | 2.0000
Default | 0.0000 | Units |
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 4
Coding | RW

See Bi-quad Filter1: a0 (04.051).

Parameter | 04.053 Bi-quad Filter1: a2
--- | ---
Short description | Used to define the a2 coefficient for a bi-quad filter to replace the low-pass filter
Mode | RFC‑A
Minimum | -2.0000 | Maximum | 2.0000
Default | 0.0000 | Units |
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 4
Coding | RW

See Bi-quad Filter1: a0 (04.051).

Parameter | 04.054 Bi-quad Filter1: b1
--- | ---
Short description | Used to define the b1 coefficient for a bi-quad filter to replace the low-pass filter
Mode | RFC‑A
Minimum | -2.0000 | Maximum | 2.0000
Default | 0.0000 | Units |
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 4
Coding | RW

See Bi-quad Filter1: a0 (04.051).

Parameter | 04.055 Bi-quad Filter1: b2
--- | ---
Short description | Used to define the b2 coefficient for a bi-quad filter to replace the low-pass filter
Mode | RFC‑A
Minimum | -2.0000 | Maximum | 2.0000
Default | 0.0000 | Units |
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 4
Coding | RW

See Bi-quad Filter1: a0 (04.051).

Parameter | 04.056 Bi-quad Filter2: a0
--- | ---
Short description | Used to define the a0 coefficient for a bi-quad filter to replace the notch filter
Mode | RFC‑A
Minimum | -2.0000 | Maximum | 2.0000
Default | 0.0000 | Units |
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 4
Coding | RW

It is possible to replace the notch filter defined by Notch Filter Centre Frequency (04.031) and Notch Filter Bandwidth (04.032) with a user defined first or second order filter. The replacement filter is a bi-quad filter. See Bi-quad Filter1: a0 (04.051) for details. This filter is set up by the following parameters.

Bi-quad Filter2: a0 (04.056) = a0
Bi-quad Filter2: a1 (04.057) = a1
Bi-quad Filter2: a2 (04.058) = a2
Bi-quad Filter2: b1 (04.059) = b1
Bi-quad Filter2: b2 (04.060) = b2

If any of these parameters are changed from their default value of zero then the internal notch filter is disabled and the coefficients in these parameters are used to define the replacement filter.

Parameter | 04.057 Bi-quad Filter2: a1
--- | ---
Short description | Used to define the a1 coefficient for a bi-quad filter to replace the notch filter
Mode | RFC‑A
Minimum | -2.0000 | Maximum | 2.0000
Default | 0.0000 | Units |
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 4
Coding | RW

See Bi-quad Filter2: a0 (04.056).

Parameter | 04.058 Bi-quad Filter2: a2
--- | ---
Short description | Used to define the a2 coefficient for a bi-quad filter to replace the notch filter
Mode | RFC‑A
Minimum | -2.0000 | Maximum | 2.0000
Default | 0.0000 | Units |
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 4
Coding | RW

See Bi-quad Filter2: a0 (04.056).

Parameter | 04.059 Bi-quad Filter2: b1
--- | ---
Short description | Used to define the b1 coefficient for a bi-quad filter to replace the notch filter
Mode | RFC‑A
Minimum | -2.0000 | Maximum | 2.0000
Default | 0.0000 | Units |
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 4
Coding | RW

See Bi-quad Filter2: a0 (04.056).

Parameter | 04.060 Bi-quad Filter2: b2
--- | ---
Short description | Used to define the b2 coefficient for a bi-quad filter to replace the notch filter
Mode | RFC‑A
Minimum | -2.0000 | Maximum | 2.0000
Default | 0.0000 | Units |
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 4
Coding | RW

See Bi-quad Filter2: a0 (04.056).

Parameter | 04.065 CTC Enable
--- | ---
Short description | Enables cyclic torque compensation system to measure or compensate for torque harmonics.
Mode | RFC‑A
Minimum | -1 | Maximum | 2
Default | 0 | Units |
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text | Description
-1 | Measure | Measure the cyclic torque harmonics.
0 | Disable | Disable the cyclic torque compensation system.
1 | Compensate | Enable the cyclic torque compensation system and actively adjust the sine and cosine harmonic components.
2 | Freeze | Enable the cyclic torque compensation system but do not actively adjust the sine and cosine harmonic components.

Cyclic torque compensation is used to assist the control system to minimise the effect of regular torque pulsations caused by the motor or the connected mechanical system. When the drive's speed controller is active, torque pulsations cause a change in motor speed which is seen in the speed feedback. The speed controller attempts to keep the speed constant by counteracting the torque pulsations, and is more effective the higher the gains and hence the bandwidth. However, it may not be desirable, or even possible, to use high enough gains to limit the speed variations to an acceptable level. The cyclic torque compensation system can use the torque reference from the output of the speed controller to assess the level of specific harmonic torque pulsations over a period of time. The harmonic torques can then be cancelled out removing the need for the speed controller to do this, and so high gains are not required. If the speed controller is not being used (i.e. torque control is selected), then the user must provide torque feedback as the input to the cyclic torque compensation system.

Cyclic torque compensation can only be enabled if the drive is operating with position feedback, i.e. Sensorless Mode Active (03.078) = 0.

CTC Enable (04.065) controls how the cyclic torque compensation system operates as given in the table below. When the drive is disabled or cyclic torque compensation is selected as "Disable", then CTC Harmonic 1 Sine Component (04.078), CTC Harmonic 1 Cosine Component (04.079), etc. are read-only and held at zero if CTC Reset On Disable (04.066) = 1 or read-write if CTC Reset On Disable (04.066) = 0.

CTC Enable (04.065) | Purpose of mode | Drive action on (CTC Harmonic 1 Sine Component (04.078), CTC Harmonic 1 Cosine Component (04.079), etc.)
Measure (-1) | Measure the harmonic torque components but do not provide any compensation for any torque disturbance. | Write (Parameters are read-only)
Disable (0) | System disabled. | Read (Parameters are read/write)
Compensate (1) | Measure the harmonic components and use them to compensate for any torque disturbance. | Write (Parameters are read-only)
Freeze (2) | Compensate for a torque disturbance using the sine and cosine components stored in the user parameters. When using this mode it may be necessary for CTC Reset On Disable (04.066) to be set to zero to prevent the sine and cosine components being reset to zero when the drive is disabled. | Read (Parameters are read/write)

Parameter | 04.066 CTC Reset On Disable
--- | ---
Short description | Causes the sine and cosine harmonic component parameters to be reset on disable.
Mode | RFC‑A
Minimum | 0 | Maximum | 1
Default | 1 | Units |
Type | 1 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW, BU

This parameter defines whether the sine and cosine harmonic components are reset to zero when the cyclic torque compensation is disabled. The system is disabled under the following conditions:

1. The drive is disabled.
2. CTC Enable (04.065) = 0.
3. CTC Mode (04.067) < 2 and Torque Mode Selector (04.011) = 2, 3 or 5.

Parameter | 04.067 CTC Mode
--- | ---
Short description | Selects whether measurements are based on the electrical or mechanical frequency, or defined individually for each channel.
Mode | RFC‑A
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text | Description
0 | Electrical | Analysis based on the electrical frequency using the torque reference output from the speed controller or torque feedback.
1 | Mechanical | Analysis based on the mechanical frequency using the torque reference output from the speed controller or torque feedback.

Electrical (0):
This method can be used to compensate for cyclic torque disturbances that are synchronous with the electrical frequency (i.e. caused by motor cogging or flux distortion, etc.). With either a synchronous motor (RFC-S mode) or asynchronous motor (RFC-A mode) the measurement and compensation system is linked to the electrical frequency of the motor. With a synchronous motor the electrical frequency is a multiple of the mechanical frequency, but with an induction motor this is not the case. Therefore torque pulsations that are caused by electrical effects cannot be compensated using "Mechanical" mode in RFC-A mode.

If the drive is operating in speed control mode (Torque Mode Selector (04.011) = 0 or 4) the output of the speed controller (Final Torque Reference (04.003)) is repeatedly analysed over an integer number of electrical cycles with an analysis period that is at least the time defined by CTC Minimum Measurement Period (04.068). The cyclic torque components are measured over each period and can be used to create a torque compensation signal to try and remove the measured torque components. The components to be removed are selected by putting the harmonic number into CTC Harmonic 1 (04.077) ... CTC Harmonic 4 (04.086). The harmonic number defines the ratio between the electrical frequency and the frequency of the component. For example, if the harmonic number is 2, then the system will attempt to remove any torque components with a frequency equal to twice the electrical frequency.

If the drive is operating in torque control (Torque Mode Selector (04.011)=1), then the torque reference created by the speed controller cannot be used, and so torque feedback must be provided in CTC Torque Feedback (04.104) to be analysed to obtain the torque components to be removed. If Torque Mode Selector (04.011) has any value other than 0, 1 or 4 cyclic torque compensation system is disabled.

If the drive is operating in speed control (i.e. Torque Mode Selector (04.011) = 0 or 4), then the phase shift between the measured input (torque reference from the speed controller) and the actual torque must be taken into account for the system to remain stable. The gain is also used so that the harmonic torque components remain approximately constant with frequency. The drive does this automatically but this does place some restrictions on the drive set-up. The drive can operate in speed control, or in position control using the AMC. The primary speed controller gains for motor map 1 must be used ( Speed Controller Proportional Gain Kp1 (03.010), Speed Controller Integral Gain Ki1 (03.011), Speed Controller Differential Feedback Gain Kd1 (03.012)). The only filter that can be used is the first order filter at the output of the speed controller and this must be set-up using Current Reference Filter 1 Time Constant (04.012). The parameters that are used to determine the correct phase shift are listed below. When the drive is operating in torque control mode these parameters are not used as the only phase correction required is to correct for the delay in the torque feedback (CTC Torque Feedback Delay (04.105)).

Speed Controller Proportional Gain Kp1 (03.010)
Speed Controller Integral Gain Ki1 (03.011)
Speed Controller Differential Feedback Gain Kd1 (03.012)
Motor And Load Inertia (03.018)
Current Reference Filter 1 Time Constant (04.012)
Torque Per Amp (05.032) / Torque Per Amp (05.032)
AMC Position Control Loop Kp Gain (39.007)
AMC Rate Selected (31.013)

Each harmonic measurement and compensation channel operates independently and completes each measurement once per cycle of the harmonic frequency subject to a minimum measurement period of CTC Minimum Measurement Period (04.068). Therefore each measurement period is completed at the end of the first harmonic period after the end of the measurement period. Each channel operates with 250us sampling, and the sample period is not affected by how many channels are enabled. Each channel can measure up to a maximum of 32767 samples and so the lowest frequency that can be measured is 1 / (32767 x 250us) = 0.122Hz. If CTC Minimum Measurement Period (04.068) is too short the measurements are affected by other harmonic components. The longer the measurement period the better the rejection of other harmonics, but the slower the system is to follow changes in the cyclic torque components. It is suggested if possible, to use a minimum period of 1.0s.

It is recommended that at least 16 samples (but preferrably more samples) are taken over each harmonic period. This defines the maximum frequency for any harmonic as 16 / 250us = 250Hz. It is possible to disable the effect of cyclic torque compensation as the harmonic frequency increases using CTC Lower Frequency Threshold (04.071) and CTC Upper Frequency Threshold (04.072). The default setting for these parameters is 250Hz so that the system never attempts to compensate for higher frequencies. As mentioned the system can estimate the phase shift between the measured torque reference and the required torque injection when the output of the speed controller is used as the input for cyclic torque compensation, however this depends on Motor And Load Inertia (03.018). If the motor and load inertia varies, then it is not possible for the drive to provide the necessary phase compensation for the system to remain stable and the compensation should be disabled by setting CTC Disable Phase Correction (04.074) which disables both gain and phase compensation between the meausred torque reference and the torque injected by the cyclic torque compensation system. If this feature is used it is necessary to disable cyclic torque compensation using CTC Lower Frequency Threshold (04.071) and CTC Upper Frequency Threshold (04.072) before the phase shift changes from -180o (which occurs at standstill) to beyond -150o. The CT Analyser PC application can be used to estimate the phase shift based on the drive set up parameters and allow the limits to be set to prevent instability.

Mechanical (1):
This method can be used to compensate for cyclic torque disturbances that are synchronous with the mechanical frequency (i.e. caused by the load). In RFC-S mode the mechanical frequency is the electrical frequency divided by the number of motor pole pairs (i.e. poles / 2). In RFC-A mode this relationship is only approximate because of the motor slip. The cyclic torque compensation system operates in the same way as described for "Electrical" mode except for the frequency of the harmonics. It should be noted that the measurement and compensation output is updated after each cycle of the harmonic frequency subject to CTC Minimum Measurement Period (04.068), and so depending on the harmonic number the update rate is once per mechanical revolution or higher. For example, the second harmonic is updated twice per mechanical revolution, the third harmonic three times per mechanical revolution, etc.

Parameter | 04.068 CTC Minimum Measurement Period
--- | ---
Short description | Defines the minimum measurement period for cyclic torque compensation.
Mode | RFC‑A
Minimum | 0.1 | Maximum | 5.0
Default | 1.0 | Units | s
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 1
Coding | RW

The cyclic torque harmonic components are measured over complete harmonic cycles. For example, if the electrical frequency is 11Hz the measurement period for the 2nd harmonic is (1 / 11Hz) / 2 = 0.045s. If CTC Minimum Measurement Period (04.068) is set to 0.1s, then the measurement and compensation has a minimum sample time of 0.1s, and so it will always include 3 cycles of the harmonic period because 2 cycles cover less than 0.1s. The longer the minimum measurement period the less effect there will be from other harmonics, but the slower the update rate of the system. There is also a minimum frequency that can be measured for each harmonic because only 32767 samples can be included. The sample rate is 250us, therefore the minimum frequency is 1 / (32767 x 250us) = 0.122Hz. If the frequency is below this level the measured harmonic components are zero.

Parameter | 04.069 CTC Gain
--- | ---
Short description | Integral gain used by the cyclic torque compensation when compensation mode is active.
Mode | RFC‑A
Minimum | 0.00 | Maximum | 0.50
Default | 0.10 | Units |
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 2
Coding | RW

This gain controls the closed-loop response of the compensation system. The compensation system performance can be approximated to a first order system with a time constant defined by

τ = CTC Minimum Measurement Period (04.068) / CTC Gain (04.069)

Parameter | 04.070 CTC Frequency Limit Mode
--- | ---
Short description | Selects the mode used when the harmonics reach their frequency limits.
Mode | RFC‑A
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text
0 | Taper
1 | Hysteresis

The frequency limits are used to disable individual harmonics from providing compensation as their frequency becomes too high. CTC Frequency Limit Mode (04.070) defines the method used to disable and enable each harmonic. It is possible to see which harmonics have been selected and whether they have been disabled by the frequency limits in CTC Active Harmonics (04.101).

Taper (0):
When compensation is active and the frequency of a harmonic exceeds CTC Lower Frequency Threshold (04.071) the values in the sine and cosine component parameters are frozen. The contribution of the harmonic to the output of the cyclic torque system is then reduced linearly to zero as the frequency increases from CTC Lower Frequency Threshold (04.071) to CTC Upper Frequency Threshold (04.072). When the frequency is above CTC Upper Frequency Threshold (04.072) the harmonic no longer contributes to the cyclic torque compensation system output. As the harmonic frequency is reduced back through the threshold region the effect on the system output is increased and the measurement system is re-enabled when the frequency falls below CTC Lower Frequency Threshold (04.071). If compensation is not active (i.e. the harmonics are only being measured), then the frequency limit does not apply.

Hysteresis (1):
When compensation is active and the frequency of a harmonic exceeds CTC Upper Frequency Threshold (04.072) the values in the sine and cosine component parameters are frozen. If the frequency subsequently falls below CTC Lower Frequency Threshold (04.071) these are again updated. If compensation is not active (i.e. the harmonics are only being measured), then the frequency limit does not apply.

Parameter | 04.071 CTC Lower Frequency Threshold
--- | ---
Short description | Lower frequency threshold below which the harmonics are measured.
Mode | RFC‑A
Minimum | 1 | Maximum | 250
Default | 250 | Units | Hz
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW, BU

See CTC Frequency Limit Mode (04.070).

Parameter | 04.072 CTC Upper Frequency Threshold
--- | ---
Short description | Upper frequency threshold for the frequency limit region.
Mode | RFC‑A
Minimum | 0 | Maximum | 250
Default | 250 | Units | Hz
Type | 8 Bit User Save | Update Rate | Background Read.
Display Format | Standard | Decimal Places | 0
Coding | RW, BU

See CTC Frequency Limit Mode (04.070).

Parameter | 04.073 CTC Maximum Harmonic Correction
--- | ---
Short description | Defines the maximum correction that can be applied for any harmonic.
Mode | RFC‑A
Minimum | 0 | Maximum | 300
Default | 10 | Units | %
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW

If harmonic compensation is active (CTC Enable (04.065) = Compensate (1) or Freeze (2)) the magnitude of each harmonic signal used for compensation is limited to the level defined by this parameter as a percentage of rated torque. This limits the values being written to CTC Harmonic 1 Sine Component (04.078), CTC Harmonic 1 Cosine Component (04.079), etc. If CTC Enable (04.065) has any other value this parameter has no effect.

Parameter | 04.074 CTC Disable Phase Correction
--- | ---
Short description | The phase correction system is used when the drive position/speed controller is active to maintain system stability. This can be disabled if the load characteristic is not known, but the cyclic torque compensation frequency range is limited.
Mode | RFC‑A
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 1 Bit User Save | Update Rate | Background Read.
Display Format | Standard | Decimal Places | 0
Coding | RW

When the drive is operating in speed control mode the cyclic torque compensation system uses the output of the speed controller to calculate the torque disturbance so that the correct compensation can be applied. It is important that this calculates the correct phase shift between the measured value and the required compensation value otherwise the system will become unstable. If the load inertia is not constant then it is not possible for the cyclic torque compensation system to calculate the phase shift. It is still possible to use cyclic torque compensation provided the compensation is disabled by the frequency limits (CTC Lower Frequency Threshold (04.071), CTC Upper Frequency Threshold (04.072)) before the change in phase shift from the phase shift at 0Hz becomes significant. If CTC Disable Phase Correction (04.074)=1 the phase shift calculation is disabled and the phase shift is a fixed at a value corresponding to 0Hz. The Cyclic Torque Compensation Application in CT Analyser can be used to show the calculated phase shift under different conditions to ensure that the it has not changed significantly before the frequency limits are reached.

This parameter has no effect unless the drive is operating in speed control mode (i.e. Torque Mode Selector (04.011) = 0 or 4) because the drive only compensates for the phase of the control system when the output of the speed controller is used as the input to the cyclic torque compensation system.

Parameter | 04.075 CTC Reverse Direction Phase Shift
--- | ---
Short description | Corrects for a possible phase shift when operating in the reverse direction.
Mode | RFC‑A
Minimum | -180 | Maximum | 179
Default | 0 | Units | °
Type | 16 Bit User Save | Update Rate | 4ms Read
Display Format | Standard | Decimal Places | 0
Coding | RW

Some electrical effects can have a different phase shift when operating in the reverse direction. For example, the 6th harmonic torque caused by motor flux distortion can include a phase shift when operating in the reverse direction. This causes the sine and cosine parameters to be different under the same operating conditions in each direction. This phase shift can be corrected by putting a non-zero value in this parameter. This is only necessary to keep the sine and cosine parameters the same in each direction and is not essential for cyclic torque compensation to work correctly. The phase shift can be calculated by running the system in the forward and reverse direction with this parameter set to zero and using the measured sine and cosine values as given below to obtain the value that needs to be entered in this parameter.

CTC Reverse Direction Phase Shift (04.075) = atan(Sine Reverse / Cosine Reverse) - atan(Sine Forwards / Cosine forwards)

Parameter | 04.076 CTC Number Of Harmonics
--- | ---
Short description | Defines the number of harmonics that are analysed by the cyclic torque compensation system.
Mode | RFC‑A
Minimum | 1 | Maximum | 4
Default | 1 | Units |
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW

CTC Number Of Harmonics (04.076) defines the number of harmonics analysed by the cyclic torque compensation system.

Parameter | 04.077 CTC Harmonic 1
--- | ---
Short description | Defines a cyclic torque harmonic to be compensated or measured.
Mode | RFC‑A
Minimum | 1 | Maximum | 40
Default | 1 | Units |
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW

CTC Harmonic 1 (04.077) defines the harmonic to be measured. This is a multiple of the electrical frequency if CTC Mode (04.067) is set to "Electrical", or a multiple of the mechanical frequency if it is set to "Mechanical". Each harmonic has a sine and cosine component parameter. For CTC Harmonic 1 (04.077) these are CTC Harmonic 1 Sine Component (04.078) and CTC Harmonic 1 Cosine Component (04.079). These components contain the information that defines the magnitude and phase of the measured harmonic component or the compensation value. The components are given as a percentage of rated torque.

Parameter | 04.078 CTC Harmonic 1 Sine Component
--- | ---
Short description | Sine component of cyclic torque harmonic 1.
Mode | RFC‑A
Minimum | -300.00 | Maximum | 300.00
Default | 0.00 | Units | %
Type | 16 Bit User Save | Update Rate | Background Read/Write
Display Format | Standard | Decimal Places | 2
Coding | RW

See CTC Harmonic 1 (04.077).

Parameter | 04.079 CTC Harmonic 1 Cosine Component
--- | ---
Short description | Cosine component of cyclic torque harmonic 1.
Mode | RFC‑A
Minimum | -300.00 | Maximum | 300.00
Default | 0.00 | Units | %
Type | 16 Bit User Save | Update Rate | Background Read/Write
Display Format | Standard | Decimal Places | 2
Coding | RW

See CTC Harmonic 1 (04.077).

Parameter | 04.080 CTC Harmonic 2
--- | ---
Short description | Defines a cyclic torque harmonic to be compensated or measured.
Mode | RFC‑A
Minimum | 1 | Maximum | 40
Default | 3 | Units |
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW

See CTC Harmonic 1 (04.077).

Parameter | 04.081 CTC Harmonic 2 Sine Component
--- | ---
Short description | Sine component of cyclic torque harmonic 2.
Mode | RFC‑A
Minimum | -300.00 | Maximum | 300.00
Default | 0.00 | Units | %
Type | 16 Bit User Save | Update Rate | Background Read/Write
Display Format | Standard | Decimal Places | 2
Coding | RW

See CTC Harmonic 1 (04.077).

Parameter | 04.082 CTC Harmonic 2 Cosine Component
--- | ---
Short description | Cosine component of cyclic torque harmonic 2.
Mode | RFC‑A
Minimum | -300.00 | Maximum | 300.00
Default | 0.00 | Units | %
Type | 16 Bit User Save | Update Rate | Background Read/Write
Display Format | Standard | Decimal Places | 2
Coding | RW

See CTC Harmonic 1 (04.077).

Parameter | 04.083 CTC Harmonic 3
--- | ---
Short description | Defines a cyclic torque harmonic to be compensated or measured.
Mode | RFC‑A
Minimum | 1 | Maximum | 40
Default | 5 | Units |
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW

See CTC Harmonic 1 (04.077).

Parameter | 04.084 CTC Harmonic 3 Sine Component
--- | ---
Short description | Sine component of cyclic torque harmonic 3.
Mode | RFC‑A
Minimum | -300.00 | Maximum | 300.00
Default | 0.00 | Units | %
Type | 16 Bit User Save | Update Rate | Background Read/Write
Display Format | Standard | Decimal Places | 2
Coding | RW

See CTC Harmonic 1 (04.077).

Parameter | 04.085 CTC Harmonic 3 Cosine Component
--- | ---
Short description | Cosine component of cyclic torque harmonic 3.
Mode | RFC‑A
Minimum | -300.00 | Maximum | 300.00
Default | 0.00 | Units | %
Type | 16 Bit User Save | Update Rate | Background Read/Write
Display Format | Standard | Decimal Places | 2
Coding | RW

See CTC Harmonic 1 (04.077).

Parameter | 04.086 CTC Harmonic 4
--- | ---
Short description | Defines a cyclic torque harmonic to be compensated or measured.
Mode | RFC‑A
Minimum | 1 | Maximum | 40
Default | 7 | Units |
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW

See CTC Harmonic 1 (04.077).

Parameter | 04.087 CTC Harmonic 4 Sine Component
--- | ---
Short description | Sine component of cyclic torque harmonic 4.
Mode | RFC‑A
Minimum | -300.00 | Maximum | 300.00
Default | 0.00 | Units | %
Type | 16 Bit User Save | Update Rate | Background Read/Write
Display Format | Standard | Decimal Places | 2
Coding | RW

See CTC Harmonic 1 (04.077).

Parameter | 04.088 CTC Harmonic 4 Cosine Component
--- | ---
Short description | Cosine component of cyclic torque harmonic 4.
Mode | RFC‑A
Minimum | -300.00 | Maximum | 300.00
Default | 0.00 | Units | %
Type | 16 Bit User Save | Update Rate | Background Read/Write
Display Format | Standard | Decimal Places | 2
Coding | RW

See CTC Harmonic 1 (04.077).

Parameter | 04.101 CTC Active Harmonics
--- | ---
Short description | Indicates which harmonics have been enabled and are active (i.e. not disabled by the frequency limit).
Mode | RFC‑A
Minimum | 0 (Display: 0000) | Maximum | 15 (Display: 1111)
Default |  | Units |
Type | 8 Bit Volatile | Update Rate | Background Write
Display Format | Binary | Decimal Places | 0
Coding | RO, ND, NC, PT, BU

The bits in CTC Active Harmonics (04.101) show which harmonics have been selected and not frozen because their frequency is above the frequency limit. Bit0 relates to Harmonic 1, Bit 1 to Harmonic 2, etc.

Parameter | 04.104 CTC Torque Feedback
--- | ---
Short description | Torque feedback should be routed to this parameter when the drive is operating in torque mode.
Mode | RFC‑A
Minimum | -300.00 | Maximum | 300.00
Default | 0.00 | Units | %
Type | 16 Bit Volatile | Update Rate | 250µs read
Display Format | Standard | Decimal Places | 2
Coding | RW

If the drive is operating in torque mode (Torque Mode Selector (04.011) = 1), then torque feedback must be provided by writing to this parameter as a percentage of rated torque. If the drive analogue inputs are used to provide this feedback, then Analog Input 1 Scaling (07.008) or Analog Input 2 Scaling (07.012) should be used to scale the input so that CTC Torque Feedback (04.104) shows the torque as a percentage of rated torque. The polarity of the torque feedback should be as though the torque is being produced by the motor, i.e., positive torque is motoring torque in the forward direction. If the measured torque has the opposite polarity, then it can be inverted using CTC Torque Feedback Invert (04.106). Normally there will be a delay between the actual torque and the measured value written to this parameter. This delay, which is used to advance the output of the cyclic torque compensation system, must be correct if compensation mode is active (CTC Enable (04.065) = Compensate(2)) otherwise the resulting phase shift can cause the system to become unstable.

If the torque feedback delay is not known then it can be measured using the cyclic torque compensation system in measure mode (CTC Enable (04.065)=-1). A torque disturbance test signal can be applied by setting CTC Test Input Level (04.108) to a non-zero value (see CTC Test Input Level (04.108) for more details). The following parameters should be recorded using the on-board scope: Torque Reference (04.008), CTC Torque Feedback (04.104) and CTC Output (04.111). With CTC Torque Feedback Delay (04.105) delay set to zero CTC Output (04.111) will be in phase with the torque feedback and delayed from the reference by the torque feedback system delay plus the delay in the drive current controllers. CTC Torque Feedback Delay (04.105) can then be increased to advance CTC Output (04.111) to be in phase with the test signal (Torque Reference (04.008)) as shown below. This will give the required setting for CTC Torque Feedback Delay (04.105).

Parameter | 04.105 CTC Torque Feedback Delay
--- | ---
Short description | Used to compensate for delay between the actual torque and the measured value being written to the torque feedback parameter.
Mode | RFC‑A
Minimum | 0.0 | Maximum | 16.0
Default | 0.0 | Units | ms
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 1
Coding | RW, BU

CTC Torque Feedback Delay (04.105) ensures that the phase of the harmonic torque components are correctly aligned when torque feedback is being used.

If CTC Feedback Remove Reference (04.107) is set to one to remove the reference from the torque feedback the delay is also used to correctly align the reference. See CTC Feedback Remove Reference (04.107) for more details.

Parameter | 04.106 CTC Torque Feedback Invert
--- | ---
Short description | This parameter is provided in case the polarity of the torque feedback is incorrect.
Mode | RFC‑A
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 1 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW

See CTC Torque Feedback (04.104).

Parameter | 04.107 CTC Feedback Remove Reference
--- | ---
Short description | If enabled this subtracts the torque reference from the torque feedback when operating in torque control mode.
Mode | RFC‑A
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 1 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW

When torque feedback is used as the input for cyclic torque compensation the system will attempt to remove all the selected harmonics present in the feedback signal. Normally these are unwanted torque components, however if the torque reference itself contains one of these components it may be a requirement to remove the unwanted part of the component created by the electrical or mechanical system, but not the component in the reference. This can be done, but is only possible if the torque feedback signal is an accurate representation of the actual torque at the harmonic frequency. If CTC Feedback Remove Reference (04.107) is set to one the reference is delayed by CTC Torque Feedback Delay (04.105) to align it with the torque feedback and then subtracted from the feedback before it is fed into the cyclic torque compensation system.

Parameter | 04.108 CTC Test Input Level
--- | ---
Short description | If this is non-zero it enables a test torque signal applied to the drive torque reference.
Mode | RFC‑A
Minimum | 0 | Maximum | 100
Default |  | Units | %
Type | 8 Bit Volatile | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW, ND, NC, PT

If CTC Test Input Level (04.108) is zero then this parameter has no effect. If it is set to a non-zero value a torque signal with a frequency equal to the electrical frequency is routed to Torque Reference (04.008) where the peak is defined by CTC Test Input Level (04.108) as a percentage of rated torque. Care should be taken not to route anything else to Torque Reference (04.008) as this will affect the test. The test signal can be used to measure the torque feedback delay (see CTC Torque Feedback (04.104)).

Parameter | 04.111 CTC Output
--- | ---
Short description | Shows the measured or compensated output from the cyclic torque compensation system.
Mode | RFC‑A
Minimum | -300.00 | Maximum | 300.00
Default |  | Units | %
Type | 16 Bit Volatile | Update Rate | 250µs write
Display Format | Standard | Decimal Places | 2
Coding | RO, ND, NC, PT

This parameter shows the combination of the torque components at the output of the cyclic torque compensation system. If CTC Enable (04.065) = Measure (-1) this shows either the combination of the torque components extracted from the selected input for the cyclic torque compensation system. If CTC Enable (04.065) = Compensate (2) or Freeze (1) this parameter shows the output of the cyclic torque compensation system being added to the torque reference.

Parameter | 04.120 Motoring Torque Limit
--- | ---
Short description | Defines the torque limit with a motoring load.
Mode | RFC‑A
Minimum | −VM_TORQUE_UNIPOLAR | Maximum | VM_TORQUE_UNIPOLAR
Default | 0.00 | Units | Nm
Type | 32 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 2
Coding | RW, VM

If either this parameter or Braking Torque Limit (04.121) are set to a non-zero value, then this parameter defines the motoring torque limit and Braking Torque Limit (04.121) defines the braking torque limit. If both this parameter and Braking Torque Limit (04.121) are left at their default value of zero the torque limits are disabled.

The torque limits are a percentage of Rated Torque (04.041), and so the rated torque must be defined for the motor otherwise if Rated Torque (04.041) is left at its default value of zero the torque limits are disabled. To ensure the torque limits are accurate it is recommended to enable the torque correction system by setting a non-zero value in Torque Correction Time Constant (04.043).

Parameter | 04.121 Braking Torque Limit
--- | ---
Short description | Defines the torque limit with a braking load.
Mode | RFC‑A
Minimum | −VM_TORQUE_UNIPOLAR | Maximum | VM_TORQUE_UNIPOLAR
Default | 0.00 | Units | Nm
Type | 32 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 2
Coding | RW, VM

See Motoring Torque Limit (04.120).

Parameter | 04.122 Motoring Power Limit
--- | ---
Short description | Defines the power limit with a motoring load.
Mode | RFC‑A
Minimum | −VM_POWER_UNIPOLAR | Maximum | VM_POWER_UNIPOLAR
Default | 0.000 | Units | kW
Type | 32 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 3
Coding | RW, VM

If either this parameter or Braking Power Limit (04.123) are set to a non-zero value, then this parameter defines the motoring power limit and Braking Power Limit (04.123) defines the braking power limit. If both this parameter and Braking Power Limit (04.123) are left at their default value of zero the power limits are disabled. The limits are limits on the motor shaft power. It should be noted that Output Power (05.003) shows the power output of the drive which include drive and motor losses which are not included in the motor shaft power.

The power limits are a percentage of rated motor shaft power which is calculated from Rated Torque (04.041), and so the rated torque must be defined for the motor otherwise if Rated Torque (04.041) is left at its default value of zero the limits are disabled. To ensure the power limits are accurate it is recommended to enable the torque correction system by setting a non-zero value in Torque Correction Time Constant (04.043).

Parameter | 04.123 Braking Power Limit
--- | ---
Short description | Defines the power limit with a braking load.
Mode | RFC‑A
Minimum | −VM_POWER_UNIPOLAR | Maximum | VM_POWER_UNIPOLAR
Default | 0.000 | Units | kW
Type | 32 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 3
Coding | RW, VM

See Motoring Power Limit (04.122).