Design of Variable Magnetization Pattern Machines for Dynamic Changes in the Back EMF Waveform

Variable magnetization pattern permanent magnet synchronous machines (VMP-PMSMs) capable of dynamic changes in the magnetization spatial distribution are discussed in this paper. VMP-PMSMs are able to change the harmonic components in the air gap magnetic flux density due to the magnet by intentional demagnetization; hence, they can effectively manipulate the torque ripples and losses according to the required operating points. The objective of this paper is to provide a procedure to design VMP-PMSMs that can have both the sinusoidal and the trapezoidal back EMF waveforms by switching magnetization pattern. The performance of the designed VMP-PMSM following the reported procedure is confirmed through experiments as well as finite element analysis (FEA) simulations in terms of the back EMF shaping, torque ripple reduction, and loss reduction. Loss analysis of VMP-PMSMs is also given as contrasting with variable flux permanent magnet machines (VF-PMSMs), showing that VMP-PMSMs can reduce more losses than VF-PMSMs with the same torque density.