Siemens SINAMICS G130 Engineering Manual page 119

The following are admissible:
a) Motors with electrically isolated winding systems in which the individual systems are not electrically
coupled and not out of phase with one another.
b) Motors with a common winding system in which all parallel windings inside the motor are interconnected
in the winding overhang or in the terminal box in such a way that they have the external appearance of one
single winding system.
The following are inadmissible:
c) Motors with electrically isolated winding systems in which the individual systems are out of phase with
one another.
d) Motors with separate winding systems on the input side which have a common, internal neutral.
Admissible and inadmissible winding systems for parallel connections of converters illustrated by the example of motors
with three parallel windings
Comments on a)
The variant with completely electrically isolated winding systems in which a separate Motor Module in the parallel
connection is assigned to each winding system should be selected where possible because
•
No decoupling measures need to be implemented at the converter output,
•
Both modulation modes, i.e. space vector and pulse-edge, can be utilized,
•
No circulating currents can develop between the systems,
•
The best possible current balance is achieved.
It is however absolutely essential for the separate winding systems to be in-phase, as the pulse patterns of the
parallel-connected Motor Modules are synchronized by the Control Unit and therefore absolutely identical.
Comments on b)
The variant with one common winding system that is fully parallel-connected inside the motor is also feasible, but has
several disadvantages as compared to variant a):
•
Decoupling measures are required.
•
Pulse-edge modulation mode cannot be utilized.
•
Circulating currents between the parallel-connected Motor Modules cannot be eliminated completely.
•
The quality of current balance between the Motor Modules in the parallel connection is not as high.
Fundamental Principles and System Description
Engineering Information
SINAMICS Engineering Manual - May 2008
© Siemens AG
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