Field weakening mode
The SINAMICS S120 converter injects a field weakening current which means that the motor
can operate above the voltage limiting characteristic without field weakening. The method
used by the converter to inject the field weakening current has a significant influence on
the curve characteristic.
Torque limit for operation on converter with field weakening option
The characteristics shown apply to operation on a SINAMICS S120 converter.
Field weakening mode is always active on a SINAMICS S120 converter.
The shape of the characteristics in field weakening mode depends on the position of
the voltage limiting characteristic. A torque/speed chart is therefore assigned to each voltage
The permissible speed range has been limited to n
recommended converter. The recommended converter is dimensioned to allow the motor
to operate in the S1(100K) mode shown. If the application requires a torque up to M
the converter selected must be capable of delivering the maximum current required to
The S1 and S3 characteristics apply to operation at the thermally permissible current. When
configuring an S3 duty cycle, you must check that the converter can deliver the peak current
required. It may be necessary to choose a larger converter.
Synchronous Motors 1FK7
Configuration Manual, (PFK7S), Edition 12.2006, 6SN1197-0AD16-0BP1
Torque characteristic of a synchronous motor operating on a converter with field
weakening (example characteristic)
shows the operating range which can be achieved with the
4.3 Field weakening mode