Design and analysis of PM-assisted synchronous reluctance machine with shifted magnetic poles

Abstract

The authors present a new design of a PM-assisted synchronous reluctance motor (PM-SynRM) with uneven air-gap length to improve the power factor and enhance the torque production capability. The rotor structure is modified to properly shift rotor magnetic poles and therefore (i) increases the back-EMF and the electromagnetic torque, (ii) allows electromagnetic torque and reluctance torque components peak near the same current phase angle. The proposed solution is simple, does not require changing the arrangement of magnets and/or flux barriers and is applicable to all types of PM-SynRMs. Sensitivity analysis is carried out to determine the extent of which the proposed magnetic pole shifting may impact the resultant torque profile. To assess the level of success, the electromagnetic characteristics of the proposed design (e.g. torque, power factor, and back-EMF) are compared against the baseline structure under the same operating conditions. For verification purposes, Finite Element simulation results are validated via a series of analytical calculations and experimental measurements, and supported with detailed theoretical discussion.