Rockwell Automation Publication 2198-UM002L-EN-P - October 2021 439
Appendix F Motor Control Feature Support
Field Weakening Mode Kinetix VPC interior permanent-magnet (IPM) motors are designed to operate
in Field Weakening mode to widen the speed range. Operation in Field
Weakening mode can result in Back EMF voltage increasing to a level that
exceeds the DC-bus voltage if a loss of control occurs. When this loss of control
occurs, the Back EMF voltage can charge the DC-bus to a level that can
overvoltage the DC-bus caps and result in a failure of the common DC-bus.
Figure 239 - Field Weakening Region
Extended Speed Feature
The Extended Speed feature is implemented in the Logix Designer application
to help prevent accidental operation at unsafe speeds. With this feature, the
controller calculates a Bus Overvoltage Speed based upon the drive's
maximum allowable bus-voltage and the Back EMF of the motor. This is the
maximum speed that does not risk damaging the drive modules in the bus
group. By default, the Extended Speed feature limits motor velocity to the Bus
Overvoltage Speed.
Continuous Operation
Peak (intermittent) Operation
Field Weakening Region
Speed (rpm)
Rated
Speed
Bus Overvoltage
Speed
Maximum
Speed
Torque (N•m)
Maximum Speed
(Kinetix VPC motors
without cooling fans)
ATTENTION: DC-bus failure can cause damage to all drive modules in the
bus group, not just the inverter connected to the Kinetix VPC motor.
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