Current Control Signal Attributes

These are the current control signal related attributes associated with a Motion Control Axis.

Current Command

The Current Command attribute represents the instantaneous value of the commanded torque producing current signal, Iq, before passing through the vector current limiter. It is tied directly to the output of the torque reference path after the 1/Kt scaling that represents the torque effort to be applied to the drive's torque producing Iq current loop. The nominal value for 1/Kt is 1 based on 100% rated torque being produced by 100% rated current.

Operative Current Limit

The Operative Current Limit attribute represents the operative current limit based on multiple limit sources.

Current Limit Source

The Current Limit Source attribute represents the operative source of a current limit when a current limit condition occurs.

Motor Electrical Angle

The Motor Electrical Angle attribute is the calculated electrical angle of the motor based on motor pole count, commutation offset, and selected feedback device.

Current Reference

The Current Reference attribute is the current reference signal, Iq, into the torque current loop summing junction.

Flux Current Reference

The Flux Current Reference attribute is the current reference signal, Id, into the flux producing current loop summing junction.

Current Disturbance

Injected torque producing current command used to excite the motor as part of the Frequency Analysis service.

Current Error

Error between commanded and actual current that is the output of the torque producing, q-axis, current loop summing junction.

Flux Current Error

Error between commanded and actual current that is the output of the flux producing, d-axis, current loop summing junction.

Current Feedback

Actual torque current applied to the axis based on current sensor feedback.

Flux Current Feedback

Actual flux current applied to the axis based on current sensor feedback.

Track Section Coil n Current Feedback

Instantaneous current measured on coil n of the track section, where n can range from one to 12.

Vq Id Decoupling Gain

Gain value that determines the amount of Iq impedance-related voltage to apply to the Vd reference signal to decouple the q-axis and d-axis current control. A Vd Iq Decoupling Gain of 100% applies the full Iq impedance voltage to the Vq reference summing junction as reflected by the Vq Decoupling signal.

Vd Iq Decoupling Gain

Gain value that determines the amount of Iq impedance-related voltage to apply to the Vd reference signal to decouple the q-axis and d-axis current control. A Vd Iq Decoupling Gain of 100% applies the full Iq impedance voltage to the Vq reference summing junction as reflected by the Vq Decoupling signal.

Lq Iq Feedback Filter Bandwidth

Value to set the bandwidth for the Iq feedback filter used to compensate for changes in Lq due to the magnetic saturation effects of PM motor types.

Flux Vector Frequency Regulator Kp

Value to set the proportional gain used by the flux vector frequency regulator for closed loop flux vector operation without a feedback device (encoderless or sensorless operation). This regulator allows the drive to maintain proper field orientation and torque producing current, Iq, by adjusting the output frequency of the drive.

Flux Vector Frequency Regulator Ki

Value to set the integral gain used by the flux vector frequency regulator for closed loop flux vector operation without a feedback device (encoderless or sensorless operation). This regulator allows the drive to maintain proper field orientation and torque producing current, Iq, by adjusting the output frequency of the drive.

Motor Stability Control Enable

Enumerated value used to enable or disable the Motor Stability Control function, which works to stabilize certain motors that are otherwise unstable when operating without a feedback device (encoderless or sensorless operation). Logix Designer does not support open loop position control. (P device function without feedback, !E). This P, !E configuration cannot be set in Logix Designer.

Motor Stability Control Filter Bandwidth

Value to set the filter bandwidth for the Iq current signal used to adjust voltage and frequency to stabilize the motor. Logix Designer does not support open loop position control. (P device function without feedback, !E). This P, !E configuration cannot be set in Logix Designer.

Motor Stability Control Voltage Gain

Value to set the gain of the voltage stability control function based on the filtered Iq current signal. Logix Designer does not support open loop position control. (P device function without feedback, !E). This P, !E configuration cannot be set in Logix Designer.

Motor Stability Control Frequency Gain

Value to set the gain of the electrical angle stability control function based on the filtered Iq current signal. Logix Designer does not support open loop position control. (P device function without feedback, !E). This P, !E configuration cannot be set in Logix Designer.

Power Device Compensation Enable

Enumerated value used to enable or disable the Power Device Compensation function, which works to compensate for power structure switching dead time, switching delay, voltage drop, and reflected wave dynamics. The Power Device Dead Time Compensation attribute adjusts dead time compensation. In rare cases, these compensation functions can result in DC offsets that increase torque ripple. In such cases, disabling Power Device Compensation can reduce the DC offset level.

Power Device Dead Time Compensation

Value that determines what percentage of the known power device switching delay to compensate for. Switching delay, if left uncompensated, can result in low-speed motor current distortion and excessive torque ripple. This problem is prevalent when controlling motors without a feedback device (encoderless or sensorless operation). Power Device Compensation must be enabled for this attribute to have any effect.

Feedback Commutation Aligned

This enumerated parameter is set to Controller Offset (1) or Database Offset (4) when the motor mounted absolute feedback device is to be aligned with the stator windings of the PM motor according to the Commutation Offset value. In some cases, the Commutation Offset can be preset to a value established by factory alignment of the motor feedback device relative to the motor stator windings. A setting of Not Aligned (0) indicates that the motor is not aligned, and that the Commutation Offset value is not valid. If the Commutation Offset is not valid, it cannot be used by the drive to determine the commutation angle. Any attempt to enable the drive with an invalid commutation angle shall result in a Start Inhibit condition. Alignment can be achieved via a Commutation Test that measures and sets the Commutation Offset for the motor or by direct user entry. If this attribute is set to Motor Offset (2), the drive derives the commutation offset directly from the motor. If set to Self-Sense (3), the drive automatically measures the commutation offset when it transitions to the Starting state for the first time after a power cycle. This generally applies to a PM motor equipped with a simple incremental feedback device.

This is a proprietary version of a new standard attribute, Commutation Alignment. Both Default and Valid Commutation Alignment values depend on the selected Feedback 1 Type as defined in the following Semantics section.

Commutation Startup Method

Specifies the method used by the drive to establish absolute rotor (or linear motor magnet track) alignment relative to stator windings (or linear motor moving coil) for the purposes of PM motor commutation when starting up the drive. If this attribute is not supported, the Feedback 1 Type selection determines the commutation startup method. Likewise, if this attribute is supported and set to From Feedback Type, the Feedback 1 Type selection also determines the commutation startup method.

The UVW startup method uses UVW signals from motor mounted encoder tracks or Hall sensors together with the Commutation Offset to align the rotor with stator windings or, in the case of a linear motor, the moving coil with the magnet track. Once aligned, commutation is maintained via position signals from the motor mounted feedback device, that is, Feedback 1.

The Digital startup method uses Digital signals from a motor mounted absolute feedback device together with the Commutation Offset to align the rotor with stator windings or, in the case of a linear motor, the moving coil with the magnet track.

The Self-Sensing start-up method applies current to the motor stator (or moving coil) during the initial Starting state to force the rotor (or moving coil) to the Null position and achieve proper commutation alignment. Once aligned, commutation is maintained via position signals from the motor mounted feedback device, Feedback 1. This method is used when there is no absolute feedback available to align the motor, for example. a motor equipped with an incremental encoder.

Commutation Offset

A value that specifies the commutation offset of the PM motor mounted feedback device in units of electrical degrees. This attribute specifies the offset from a commutation reference position defined by applying DC current into the A terminal and out of the shorted B and C terminals of the motor and allowing the rotor to move to its magnetic null position relative to the stator. On an absolute encoder or resolver, the offset is the difference from the device’s zero absolute position and the commutation reference position. On an incremental encoder or Hall sensor with UVW signals, the offset is the difference between the position corresponding to a transition of the commutation device’s W (S3) channel (with the U (S1) channel high and the V (S2) channel low) and the commutation reference position. The commutation offset is only applicable to the motor mounted Feedback 1 device.

When the optional Commutation Alignment attribute is supported and set to Controller Offset or Database Offset, the drive applies the Commutation Offset value from the controller to determine the electrical angle of the motor. In this case, a valid Commutation Offset value must be entered by the user, read from the Motor Database, or determined by the Commutation Test. In the unusual case where the commutation offset is also stored in the motor and differs significantly from the Commutation Offset value from the controller, the drive shall transition to the Start Inhibited state.

If the Commutation Alignment attribute is not set to Controller Offset or Database Offset, the drive ignores the Commutation Offset value from the controller and the drive must determine its internal commutation offset value by other means. Without a valid commutation offset, the drive shall be Start Inhibited.

Commutation Self-Sensing Current

When a PM motor feedback drive device is an incremental encoder without UVW tracks for commutation, a Self-Sensing algorithm is run during the Starting state that determines the Commutation Offset to apply to the position feedback. This algorithm applies a current to the motor stator to orient the rotor to establish the motor commutation phasing.

Commutation Polarity

When a PM motor is using UVW signals for commutation startup, it is critical that the UVW phases of the commutation device follow the phasing of the motor. Normal polarity implies UVW phasing according to factory specification when the commutation device is moving in the factory defined positive direction. Inverted polarity effectively switches the UVW phasing to UWV thus reversing the directional sense of the commutation device. If it is determined via a Commutation Test that the phasing of the motor and the phasing of the commutation device have opposite polarity, this attribute can be used to compensate for the mismatch.

Commutation Alignment

This enumerated parameter is set to Controller Offset (1) or Database Offset (4) when the motor mounted absolute feedback device is to be aligned with the stator windings of the PM motor according to the Commutation Offset value. In some cases, the Commutation Offset can be preset to a value established by factory alignment of the motor feedback device relative to the motor stator windings. A setting of Not Aligned (0) indicates that the motor is not aligned, and that the Commutation Offset value is not valid. If the Commutation Offset is not valid, it cannot be used by the drive to determine the commutation angle. Any attempt to enable the drive with an invalid commutation angle shall result in a Start Inhibit condition. Alignment can be achieved via a Commutation Test that measures and sets the Commutation Offset for the motor or by direct user entry. If this attribute is set to Motor Offset (2), the drive derives the commutation offset directly from the motor. If set to Self-Sense (3), the drive automatically measures the commutation offset when it transitions to the Starting state for the first time after a power cycle. This generally applies to a PM motor equipped with a simple incremental feedback device.

Both Default and Valid Commutation Alignment values depend on the selected Feedback 1 Type as defined in the Semantics section.

Commutation Offset Compensation

This value specifies the change in the Commutation Offset value in units of electrical degrees as a linear function of current. When the Iq current is +100% of rated continuous current, the Commutation Offset value is decreased by the value of this attribute. When the Iq current is -100%, the Commutation Offset is increased by the value of the attribute. This attribute is used by the drive to compensate for changes in the optimal Commutation Offset angle that can occur as a function of motor current.