Siemens SINAMICS G120 Operating Instructions Manual page 208

Functions
8.9 Application-specific functions
DC braking when the start speed for DC braking is fallen below
DC braking is automatically activated as soon as the motor speed falls below the start speed
for DC braking. However, the motor speed must have first exceeded the start speed for DC
braking. Once the DC braking time is complete, the inverter switches to normal operation. If
p1230 is set to 0, DC braking can also be canceled before the time defined in p1233.
DC braking when a fault occurs
If a fault occurs, where the configured response is DC braking, then the inverter first brakes
the motor along the down ramp until the start speed for DC braking is reached, and then
starts DC braking.
Activating DC braking independent of the speed using a control command
DC braking starts independent of the motor speed, as soon as the control command for
braking (e.g. via DI3: P1230 = 722.3) is issued. If the braking command is revoked, the
inverter returns to normal operation and the motor accelerates to its setpoint.
Note: The value of p1230 is displayed in r1239.11.
DC braking when the motor is switched off
If the motor is switched off with OFF1 or OFF3, the inverter first brakes the motor along the
down ramp until the start speed for DC braking is reached, and then starts DC braking. The
motor is then switched into a torque-free condition (OFF2).
Note
In the following operating modes, it is possible that the motor is still rotating after DC braking.
This is the reason that in these operating modes "Flying restart" must be activated:
• DC braking when the start speed for DC braking is fallen below
• Activating DC braking independent of the speed using a control command
• DC braking when the motor is switched off
The DC braking function can only be set for induction motors.
DC braking converts some of the kinetic energy of the motor and load into heat in the motor
(temperature rise). The motor will overheat if the braking operation lasts too long or the
motor is braked too often.
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CAUTION
Operating Instructions, 01/2011, FW 4.4, A5E02999804A AB
SINAMICS G120C Inverter