Rockwell Automation 20G PowerFlex 750-Series AC Drives - Manual (Page 216)

216 Rockwell Automation Publication 750-RM002B-EN-P - September 2013
Chapter 4 Motor Control
Flux Braking Flux Braking is an independent feature from the P370/371 [Stop Mode A/B]
available in PowerFlex 750-Series drives. When enabled, flux braking is active
during the decel ramp of a speed change. Flux braking changes the Volts per
Hertz curve ratio outputting a higher voltage, relative to the normal V/Hz curve,
to the motor causing over fluxing thus reducing the speed faster than just the
decel ramp alone. This feature is not intended for high inertia loads because over
fluxing can cause excessive heating in the motor. Very long decel times can build
heat.
Flux Braking works in all motor control modes.
Table 11 - Flux Braking Parameters
Traces
In all of the following plots the Accel/Decel times are 0.5 s. P372/373 [Bus Reg
Mode A/B] is set to option 1 “Adjust Freq.” There is a fair amount of inertia
connected to the motor shaft. P370/371 [Stop Mode A/B] is set to 1 “Ramp” to
stop.
In the plot below the Flux Braking feature is disabled. Note the decel time. Here
the bus regulator is controlling the stop time.
Number Parameter Name Min / Max Default
388 Flux Braking En Disabled / Enabled Disabled
389 Flux Braking Lmt 100.00 / 250.00 % 125.00
390 Flux Braking Ki 0.0 / 1000000.0 10000.0
391 Flux Braking Kp 0.0 / 1000000.0 0.0 (Disabled)
Flux Braking - Disabled
Id Torque Ref Motor Speed DC Bus Voltage
No change in flux to the motor.