Rockwell Automation 1336E IMPACT Adjustable Frequency AC Drive User Manual V 1-4.XX - Manual (Page 146)

9-6 Applications
In a few applications (typically greater than 200HP), the flux braking
may interact with the field weakening control. This may result in a
bus overvoltage fault. If this occurs, increase Decel Time 1
(parameter 44) and/or Decel Time 2 (parameter 45) as needed.
Because flux braking increases motor losses, the duty cycle used with
this method must be limited. Check with the motor vendor for flux
braking or DC braking application guidelines. You may also want to
consider using external motor thermal protection.
Using DC Braking
DC braking only becomes active during a stop (not including coast
stop) and is not active during normal decelerations. Other stopping
methods may perform better depending on the motor and the load
being stopped.
To enable DC braking:
1. Set bit 9, DC Brake, in Bus/Brake Opts (parameter 13).
2. Clear bit 10, Brake/Regen, in Bus/Brake Opts.
3. Clear bit 5, Bus High Lim, in Bus/Brake Opts.
When DC braking is enabled and you command a stop, DC current is
applied to the motor. This increases motor losses and may result in a
shorter motor deceleration time. DC Brake Current (parameter 79)
controls the magnitude of DC current applied. The magnitude has a
maximum range of 70% of the drive rated current. Current limit and
IT protection (for times greater than 60 seconds) can further reduce
the applied DC Brake Time (parameter 80). Typically, you will
measure the stopping time that you should enter in DC Brake Time.
Because DC braking increases motor losses, the duty cycle of
stopping with this method must be limited. Check with the motor
vendor for DC braking application guidelines. You may also want to
consider using external motor thermal protection.
You can use DC hold when the 1336 IMPACT drive is set up for
encoderless operation and some level of resisting torque is desired at
near zero speed.
Using DC Hold After the motor is stopped, DC current is applied to the motor.
Although speed and torque are not controlled, the DC current results
in resisting torque when the motor shaft is rotated. As the motor speed
increases towards the rated slip for the motor, a very high resisting
torque can be produced.
Only use DC hold for encoderless operation where torque control at
zero speed cannot be guaranteed. For encoder operation, full torque
and speed control is provided at zero speed and you should use the
normal torque or speed controls.
file: Application
group: DC Braking/Hold