Features of Operation of Induction Motors with a Combined Winding in a Frequency-Controlled Electric Drive

Abstract

An increase in losses and electromagnetic noise of induction motors and wave overvoltages when a motor is operating from a frequency converter with pulse-width modulation of voltage due to higher temporary harmonics of voltage and current to a certain extent can be compensated by the use of combined windings, which reduce differential dissipation and inductive reactance, weakening of wave overvoltages, additional losses, and electromagnetic noise from a magnetic field’s higher spatial harmonics. The use of a combined winding with a doubled number of parallel structures when connecting the star and triangle (D connection) windings in parallel in frequency-controlled asynchronous motors makes it possible to use thinner wires and to reduce additional losses and displacement of current by higher temporary harmonics of a current. Parameters of combined windings must be selected based on a refined analysis of electromagnetic processes due to the possibility of the occurrence of equalizing currents in the circuits between the phases of different windings. An algorithm for the interaction of coupled circuit electromechanical and field electromagnetic models is proposed, which allows for refined modeling of an operation of induction motors with combined windings from a frequency converter with pulse-width modulation of voltage. When connecting the star and triangle circuits in series in a combined winding, compared to a three-phase winding, the pattern of voltage pulses, the initial and final pulse voltage distributions along the turns change, and the potential operating conditions of a winding are improved.