Field Weakening View

The field weakening settings are nested under the Motor section of the View Tree. This view lets you configure the field weakening loop.

Element Description Command
Field Weakening This field allows a rotary permanent magnet motor to operate above rated speed. AXIS#.MOTOR.FIELDWEAKENING
Voltage Threshold

This field determines the field-weakening loop’s threshold voltage with respect to the bus voltage in [%]. By default, this value is set to 95%, meaning if the magnitude of the motor-voltage vector tries to go above 95% of bus voltage, the field weakening algorithm activates. Once activated, it maintains the motor-voltage vector magnitude at 95% of bus voltage. It applies whatever d-axis current necessary to reduce the induced back-emf-voltage of the motor to create the commanded q-axis current.

  • Setting this value to higher than 95% means having less voltage margin for the voltage regulation but results in higher voltage utilization.
  • Setting this value to lower than 95% means having higher voltage margin for the voltage regulation but results in lower voltage utilization.
 AXIS#.FIELDWEAKENING.VBUSMARGIN
Loop BandwidthClosedIn computer networking, bandwidth often refers to a data rate measured in bits/s, for example, network throughput. The reason for the connection of data rate with the term bandwidth is that the limit to the data rate of a physical communication link is related to its bandwidth in hertz

Thid field determines the field-weakening-loop’s bandwidthClosedIn computer networking, bandwidth often refers to a data rate measured in bits/s, for example, network throughput. The reason for the connection of data rate with the term bandwidth is that the limit to the data rate of a physical communication link is related to its bandwidth in hertz when entering the above-base-speed region.


  • The field weakening control loop is a nonlinear loop and the bandwidth increases as velocity increases. Always allow for 50% increase in the bandwidth.

To correctly set the internal parameters of the field weakening loop, based on the commanded bandwidth, the following motor parameters must be set correctly:

 AXIS#.FIELDWEAKENING.LOOPBW
Voltage Filter Bandwidth

This field determines the bandwidth of the second order low-pass biquad filters that are applied on the q-axis and d-axis voltages for noise reduction.

These voltages are used inside the field weakening algorithm for regulating the motor-voltage-vector-magnitude when operating above base speed. Lower bandwidths result in cleaner signals but can also create phase lag and lower the phase margin of the system. Depending on the required speed of the motion, they can be adjusted.

 AXIS#.FIELDWEAKENING.VOLTFILTER
Current Filter Bandwidth

This field determines the bandwidth of the second order low-pass biquad filters that are applied on the q-axis and d-axis currents for noise reduction.

These currents are used inside the field weakening algorithm for regulating the motor-voltage-vector-magnitude when operating above base speed. Lower bandwidths result in cleaner signals but can also create phase lag and lower the phase margin of the system. Depending on the required speed of the motion, they can be adjusted.

 AXIS#.FIELDWEAKENING.CURRFILTER

See Field Weakening for more information.