Rockwell Automation Publication 2198-UM002E-EN-P - February 2018
365
Motor Control Feature Support
Appendix D
Field Weakening Mode
Kinetix VP (Bulletin 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 186 - 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
To
rq
ue
(N
•m)
ATTENTION:
DC-bus failure can cause damage to all drive modules in the
bus group, not just the inverter connected to the Bulletin VPC motor.