Rockwell Automation 20C PowerFlex 700H Drives Programming User Manual
Page 102
102
Rockwell Automation Publication 20C-PM001F-EN-P - March 2012
Appendix B
Application Notes
DC Brake
This method uses DC injection of the motor to Stop and/or hold the load.
1. On Stop, 3 phase drive output goes to zero (off)
2. Drive outputs DC voltage on the last used phase at the level programmed in [DC Brake Level] Par 158.
This voltage causes a “stopping” brake torque. If the voltage is applied for a time that is longer than the
actual possible stopping time, the remaining time will be used to attempt to hold the motor at zero
speed.
3. DC voltage to the motor continues for the amount of time programmed in [DC Brake Time] Par 159.
Braking ceases after this time expires.
4. After the DC Braking ceases, no further power is supplied to the motor. The motor may or may not be
stopped. The drive has released control.
5. The motor, if rotating, will coast from its present speed for a time that is dependent on the mechanics of
the system (inertia, friction, etc).
Ramp
This method uses drive output reduction to stop the load.
1. On Stop, drive output will decrease according to the programmed pattern from its present value to zero.
The pattern may be linear or squared. The output will decrease to zero at the rate determined by the
programmed [Maximum Freq] and the programmed active [Decel Time x]
2. The reduction in output can be limited by other drive factors such as such as bus or current regulation.
3. When the output reaches zero the output is shut off.
4. DC voltage is applied to the motor for a time equal to [DC Brake Time] at [DC Brake Level].
Hold
This method combines two of the methods above. It uses drive output reduction to stop the load and DC
injection to hold the load at zero speed once it has stopped.
1. On Stop, drive output will decrease according to the programmed pattern from its present value to zero.
The pattern may be linear or squared. The output will decrease to zero at the rate determined by the
programmed [Maximum Freq] and the programmed active [Decel Time x]
2. The reduction in output can be limited by other drive factors such as bus or current regulation.
3. When the output reaches zero 3 phase drive output goes to zero (off) and the drive outputs DC voltage
on the last used phase at the level programmed in [DC Brake Level] Par 158. This voltage causes a
“holding” brake torque.
4. DC voltage to the motor continues until a Start command is reissued or the drive is disabled.
5. If a Start command is reissued, DC Braking ceases and he drive returns to normal AC operation. If an
Enable command is removed, the drive enters a “not ready” state until the enable is restored.
Mode
Description
Stop
Command
DC Brake Time
(A)
(C)
(B)
Time
Output Voltage
Output Current
Motor Speed
DC
Brake Level
DC BrakeTime
DC
Brake
Level
Stop
Command
Time
Output Voltage
Output Current
Motor Speed
Output Voltage
Output Current
Zero
Command
Speed
DC
Brake Level
Time
Output Voltage
Output Voltage
Output Current
Output Current
Motor Speed
Output Voltage
Output Current
Motor Speed
Re-issuing a
Start Command
Stop
Command
Zero
Command
Speed