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Sensorless Control for Synchronous Motors (S300-S700)

Valid for S300, S700
- From firmware 5.06 for special motors
- Firmware planned for all motors


If a synchronous motor is run without feedback (sensorless) on S300 / S700, there are two control procedures that are used for different speeds.

In all sensorless modes, the output frequency is limited to 599 Hz. If your application requires a higher output frequency, please contact our support.

Low speeds

The step motor procedure is used to achieve a high starting torque. In this procedure, a current is forced to the motor via a space vector.

Read / Write parameters

MIMR xx – Current in amperes, e.g. 10A at speed >0  (25% at zero speed)
SLTSWITCH x – Time  in stepper mode, e.g. 400 (ms)
SLACCMAX x– Ramp (caution: not in SI units), e.g. 100

Read parameters (scope)

in association with

High speeds

At higher speeds there is a switch to vector control. When using this control, the speed is recorded and controlled via the current sensor system. The current increases in direct proportion to the torque.

Read / Write parameters

SLIQK zzz - Vector compensation +/- e.g.: 200
SLIDK01 zzz Gain for motor adjustment
MVR zzz – Final motor speed.
GV, GVTN, ACC and DEC are active
TIP: MRESBW to values lower than 100

Read parameters (scope)

ISLQ - Compensation quality – This value can be optimized using SLIQK
DELTAERR – Error which is controlled – Minimize estimated orientation error
V_ACT – Estimated speed
ISLD – D Components for delta error – D voltage'
ISLQ– Q components for delta error – Q voltage

Thermosensor monitoring

SLTEMPM 0 – Temperature sensor is not monitored in sensorless operation (FBTYPE 10). Default
SLTEMPM 1– Temperature sensor is monitored in sensorless operation (FBTYPE 10).


Lars Kühn's picture
Lars Kühn