Analysis of harmonic contents in induced voltage and electromagnetic torque in interior permanent magnet synchronous machines under loaded condition

Permanent magnet synchronous motor (PMSM) is often characterized by open and short circuit measurements of voltages and currents to determine back-emf/torque constant and inductive reactances. Such single point measurements of machine parameters are quite often inadequate for estimating motor performances in particular torque ripple under loaded condition for low torque ripple applications. In addition, the effect of armature reaction as the load increases introduces further inaccuracies for generating appropriate control commands. This research is directed to understand the behavior of the machine under loading condition and treat the no-load condition as a special case where the current in the motor is zero. The findings will be extended to explain the harmonic contents in induced voltage, inductive reactance and the overall effect on electromagnetic torque. The theoretical findings are supported by test results.