Siemens SINAMICS S120 Function Manual page 215

DC brake (induction motors)
The DC brake is activated via the parameter p1231 = 4. It can be triggered via an input
signal p1230 (signal = 1) or a fault response.
Activation of DC brake by BI
If the DC brake is activated by the digital input signal, the first step is that the pulses are
blocked for the demagnetization time p0347 of the motor in order to demagnetize the motor -
the parameter p1234 "Speed at the start of DC braking" is ignored.
Then the DC brake, braking current p1232 is applied as long as the input is initiated in order
to brake the motor or hold it at standstill.
If the DC brake is removed, the drive returns to its selected operating mode.
The following is applicable:
● With servo (controlled with encoder):
● With vector control (controlled with or without encoder):
● In V/f mode:
DC brake as a fault response
If the DC brake is activated as a fault response, the motor is initially braked in field-oriented
mode along the braking ramp up to the threshold set in p1234. The slope of the ramp is
identical with that of the OFF1 ramp (parameterized using p1082, p1121). Subsequently, the
pulses are disabled for the motor demagnetizing time p0347 in order to demagnetize the
motor. The DC braking will start for the duration set in p1233.
If an encoder is used, braking will continue until the speed falls below the standstill threshold
p1226.
If no encoder is used, only the period in p1233 will be applied.
Drive functions
Function Manual, (FH1), 10/2008, 6SL3097-2AB00-0BP5
6.9 Armature short-circuit brake, internal voltage protection, DC brake
The drive returns to field-oriented control after the demagnetization time has elapsed
(p0347 can also be set to 0). Limitations apply in case of extreme field weakening.
The drive is synchronized with the motor frequency if the "Flying restart" function is
activated, and
the drive then returns to controlled mode. If the "flying restart"
function is not active, the drive can only be restarted from standstill without an
overcurrent fault.
With the "flying restart" function activated, the converter frequency is synhronized with
the motor frequency, and the drive will then return to V/f mode. If
the "flying restart" function is not available, the drive can only be restarted from standstill
without overcurrent fault.
Basic functions
215