Torque analysis and stator windings influence research on negative-salient permanent magnet synchronous motor

Abstract

Compared with the traditional motor, the negative-salient permanent magnet synchronous motor (NSPMSM) has the characteristics of wide-speed range, strong overload capacity and uneasily demagnetized permanent magnet. In this paper, a new rotor structure of NSPMSM is proposed by using magnetic bridge to increase the d-axis inductance (Ld) and W-type permanent magnet to decrease the q-axis inductance (Lq). Firstly, the electromagnetic torque performance of NSPMSM was analyzed from the parameters of permanent magnet (PM) thickness, magnetic bridge length, eccentricity distance and air-gap length using finite element method. At the same time, the electromagnetic torque ripple and cogging torque of the NSPMSM are further analyzed, which provides an effective basis for evaluating the optimal performance of the NSPMSM. Secondly, the effects of different stator slots and different winding layers on the air-gap magnetic flux density, electromagnetic torque, power and eddy current loss of PM of the NSPMSM were analyzed by finite element method under the condition of same rotor. The advantages and disadvantages of different windings are summarized, and the constant-power speed range of the NSPMSM is calculated, which provides the basis for the study of the flux weakening properties of the new motor. The results of theoretical analysis agree with those of simulation analysis, which verifies the effectiveness and feasibility of the new motor.