Asynchronous motor fed from converter with torque control - converts motor into generator by current reduction and changing slip from positive to negative

摘要

The asynchronous motor (4) is fed from a convertor (3) and has a circuit for controlling the torque. The circuit compares the slip frequency (f2) with a frequency (fn) that is proportional to the speed of the motor to produce a difference in order to control the convertor. The slip frequency (f2) is kept constant to a fixed value which is independent of the constant maximum torque. The torque is thus only controlled by the constant slip frequency above a given value. The slip frequency is increased to a given value which lies above the weakness range of the field. The motor can be converted into a generator by first reducing the nominal value of the current and changing the slip frequency from a positive value to a negative value.