Siemens SINAMICS G120P, Operating Instructions Manual

Page: 356 / 496

Functions
7.5 Motor control
Inverter cabinet units
356
Operating Instructions, 12/2014, A5E32923362A
7.5 Motor control
7.5.1 Vector control or V/f control
Criteria for selecting either V/f control or vector control
Motors should preferably be operated in vector control.
When compared to V/f control, vector control offers the following advantages because of the
sensoress actual speed acquisition:
● The speed is more stable for motor load changes.
● Shorter accelerating times when the setpoint changes.
● Acceleration and braking are possible with an adjustable maximum torque.
● Improved protection of the motor and the driven machine as a result of the adjustable
torque limiting.
● Full torque is possible at standstill.
It is not permissible to use vector control in the following cases
● If the motor is too small in comparison to the inverter (the rated motor power must not be
less than one quarter of the rated inverter power).
● If you operate several motors on one inverter.
● If a power contactor is used between the inverter and motor, and is opened while the
motor is powered up.