Dc Braking/Combined Braking - Siemens 3RW44 Manual

7.3.3

DC braking/combined braking

In the case of DC braking or combined braking, coasting down or the natural run-down of the
load is shortened.
The soft starter imposes a (pulsating) direct current in phases L1 and L3 on the motor stator.
This current generates a permanent magnetic field in the stator. Since the rotor is still
rotating due to its mass inertia, currents are induced in the short-circuited rotor winding that
generate a DC braking torque.
Note
The DC braking/combined braking stopping function is not possible in inside-delta circuits.
Note
The pulsating direct current loads the system asymmetrically and the motor and the feeder
must be designed for the higher current load during the stopping procedure. It may be
necessary to overdimension the soft starter.
Note
Two braking variants are available:
Combined braking:
Use the combined braking function if applications with small mass inertias (centrifugal
masses) are to be stopped (J
operations when the combined braking function is applied. Use the DC braking function if a
uniformly long braking time is to be achieved.
DC braking:
Use the DC braking function if applications with small mass inertias (centrifugal masses) are
to be stopped (J
braking function.
Risk of property damage.
For optimum motor protection, the combination of electronic motor overload protection and
evaluation of a temperature sensor installed in the motor is recommended.
Combined braking coasting method
When the combined braking coasting method is chosen, the dynamic braking torque, DC
braking torque and coast-down time can be set on the starter.
Dynamic braking torque
The dynamic braking torque determines the braking effect at the start of the braking process
to reduce the speed of the motor. The braking process is then continued automatically using
the DC braking function.
3RW44 soft starters
Manual, 03/2017, NEB535219502000/RS-AB/008
≤ 5 x J
load motor
CAUTION
≤ J ). The real coast-down time can vary during braking
load motor
). An external braking contactor is required for the DC
Device functions
7.3 Coasting methods
131