Design and Analysis of a Variable-Flux Pole-Changing Permanent Magnet Memory Machine

This paper proposes a new topology of a variable-flux pole-changing permanent magnet (PM) memory machine. The fractional-slot concentrated windings are employed in the stator side, which can increase the utilization ratio of winding under different pole modes. The neodymium-iron-boron PM poles and aluminum-nickel-cobalt (AlNiCo) PM poles are hybridized in the rotor side. The proposed machine features the capability of its pole number to switch back and forth between six poles and two poles through changing the magnetization directions of AlNiCo PMs via the stator winding. Besides, the air gap flux can be flexibly adjusted by varying the amplitudes of magnetization current pulses. The topology and design principle of the machine are described in detail, and the electromagnetic characteristics, including magnetic field distributions, air-gap flux density, as well as back electromotive force (EMF), in different operation modes are computed using a finite-element method. Due to the existence of the fifth harmonic component of back EMF, the torque quality is improved through injecting the fifth harmonic current under different magnetized levels of AlNiCo PMs. Besides, the field regulation capabilities in both the pole modes are analyzed.