Harmonics and inter-harmonics of voltage converter supplied induction machine stator currents

Abstract

The paper contains waveforms of currents for the direct and voltage source inverter supplied induction machine, with account for harmonics and inter-harmonics. By direct supply the grid is assumed to be either purely sinusoidal or polluted by 3rd, 5th and 7th harmonics. The voltage inverter operates in a PWM mode. Special model of the machine accounts for true dependencies of stator and rotor inductances versus rotor angle, resulting from air gap magnetic flux distribution. Calculations of true derivatives of inductances, with respect to rotor angle, allowed for calculation of electromagnetic torque and, in consequence, the machine's dynamics, with allowance for speed fluctuation in steady state operation.