Method for reducing mains system harmonics when controlling electrical motors

摘要

The electrical motor (4) is controlled by a control stage (3, 6, 16) supplied from a d.c. link circuit (2) containing a buffer capacitor (C). The d.c. link is supplied from a rectifier (1) connected to an a.c. system. In synchronism with the a.c. system frequency (fNetz) the control stage briefly interrupts the operation of the motor during the time the capacitor is being charged. During this period the motor can act as a generator and feed back an additional charging current to the capacitor. The electrical motor can be an induction motor with a frequency converter as the control stage.