Stop modes – Rockwell Automation 20B PowerFlex 70, PowerFlex 700 Reference Manual User Manual
Page 197
Stop Modes
Rockwell Automation Publication PFLEX-RM001H-EN-P - June 2013
197
Stop Modes
[Stop Mode A, B]
[DC Brake Lvl Sel]
[DC Brake Level]
[DC Brake Time]
1. Coast to Stop
- When in Coast to Stop, the drive acknowledges the Stop
command by shutting off the output transistors and releasing control of the
motor. The load/motor will coast or free spin until the mechanical energy is
dissipated.
2. Dynamic Braking
FLEX-AT001
.
3. DC Brake
is selected by setting [Stop Mode A] to a value of “3.” The user can
also select the amount of time the braking will be applied and the magnitude
of the current used for braking with [DC Brake Time] and [DC Brake Level].
This mode of braking will generate up to 40% of rated motor torque for
braking and is typically used for low inertia loads.
When in Brake to Stop, the drive acknowledges the Stop command by
immediately stopping the output and then applying a programmable DC
voltage [DC Brake Level] to 1 phase of the motor.
The voltage is applied for the time programmed in [DC Brake Time]. After
this time has expired, all output ceases. If the load is not stopped, it will
continue to coast until all energy is depleted (A on the diagram below). If the
time programmed exceeds the needed time to stop, the drive will continue to
apply the DC hold voltage to the non-rotating motor (B on the diagram
below). Excess motor current could cause motor damage. The user is also
cautioned that motor voltage can exist long after the Stop command is issued.
The right combination of Brake Level and Brake Time must be determined to
provide the safest, most efficient stop (C on the diagram below).
Coast Time is load dependent
Stop
Command
Time
Output Voltage
Output Current
Motor Speed
Stop
Command
DC Hold Time
(A)
(C)
(B)
Time
Output Voltage
Output Current
Motor Speed
DC
Hold Level