Advanced commissioning
6.15 Motor control
Converter with the control units CU240D-2
Operating Instructions, 04/2018, FW V4.9 SP10, A5E34262100B AF
213
6.15.2.7
Pole position identification
The pole position of a synchronous motor
The pole position of a synchronous motor is the deviation between the
magnetic axis in the rotor and the magnetic axis in the stator.
The image below shows you the pole position of a synchronous motor
in a simplified cross-section.
The inverter must know the pole position of the rotor in the motor in order to be able to
control the torque and speed of a synchronous motor.
Pole position identification
The inverter must measure the pole position for motors not equipped with an encoder, or for
encoders, which do not supply the information regarding the pole position.
If you are using a Siemens motor, then the inverter automatically selects the appropriate
technique to determine the pole position, and when required starts the pole position
identification.
Motor without an encoder
Each time the motor is switched on (ON/OFF1 command),
the inverter measures the pole position.
As a result of the measurement, the motor responds to an
ON command with a delay of up to 1 second. The motor
shaft can rotate slightly during the measurement.
Identifying the pole position
using a measurement
