Applying a control unit to an asynchronous machine which is operated without a rotary encoder

Abstract

Exemplary embodiments provide a method for connection or application of a converter to a rotating asynchronous machine which is operated without an encoder, without a high current and without a torque surge. The method provides a control unit, using an inverter or converter, for feeding the asynchronous machine which rotates at a mechanical rotary speed. The asynchronous machine is regulated by the control unit. A stator current vector is ascertained from measured currents of the stator windings of the asynchronous machine and a rotating stator voltage vector. Calculation is effected in respect of a stator flux change vector from the stator current vector, the stator voltage vector and a stator resistance in accordance with a motor model. An angle difference between the stator current vector and the stator flux change vector is calculated. That angle difference is regulated to a reference value of 90° or −90°, wherein an output signal of the regulator corresponds to a rotary field frequency, to be impressed, of the voltage vector of the stator. Regulation is effected in respect of an amplitude of the stator voltage vector by way of a current regulator to which the difference of a current reference value and a parameter corresponding to the amplitude of the stator current is made available at the input as a regulating difference.