Parallel Connection Of Power Units - Siemens Sinamics S120 Function Manual

Vector control with encoder for parallel-connected drives functions in the same way as for a
single drive if the drives are coupled via the load and the speeds do not differ by more than
the working-point-dependent pull-out slip.
Counter-example:
The gear ratios used to couple the motors with the load are large and the backlash and
elasticity in the drive train are therefore high. If the load then causes one of the motors to
rotate, but the other is still stationary, the drive without an encoder will stall.
If a motor is defective, the individual motor will be shut down on overcurrent by the motor
circuit breaker. The power unit will be shut down by the control (if available) or, in the case of
a turn-to-turn fault in the motor, the power unit will go into the fault condition. The motor must
then be decoupled from the parallel grouping. Parameter p0306 is changed by the
DDS/MDS changeover.
Overview of important parameters (see SINAMICS S120/S150 List Manual)
● p0300[0...n] Motor type
● p0306[0...n] Number of motors connected in parallel
● p0307[0...n] Rated motor power
● p0640[0...n] Current limit
● p2002 Reference current
7.11

Parallel connection of power units

In order to extend the power range, SINAMICS S120 supports the parallel connection of
identical power units such as Line Modules and/or Motor Modules. The prerequisites for
connecting power units in parallel are as follows:
● Same type
● Same type rating
● Same rated voltage
● Same firmware version
● Chassis or cabinet format
● The Motor Modules must be operated in vector control
It makes sense to connect Line Modules and Motor Modules in parallel for the following
reasons:
● To boost the converter output if it is not technically or economically feasible to achieve
● To increase the availability, for example, to maintain emergency operation (possibly also
Drive functions
Function Manual, (FH1), 01/2012, 6SL3097-4AB00-0BP2
the required power by any other means.
at a lower rating), if a power unit fails.
Function modules
7.11 Parallel connection of power units
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