Equivalent Magnetic Circuit Analysis of Doubly Salient PM Machine With Π-Shaped Stator Iron Core Segments

An equivalent magnetic circuit (EMC) analytical method for a 3-phase doubly salient permanent magnet (DSPM) machine with Π-shaped stator iron core segments (Π-core DSPM machine) is presented in this paper. This method is based on the airgap field modulation theory. First, the airgap permeance of the doubly salient machine is calculated, based on which the influence of slotting on modulation effect is analyzed. Then, an EMC model of this machine is established according to its main magnetic field distribution. Considering the slotting effect on the average airgap flux density, Carter's coefficient is used to calculate the equivalent airgap length and the airgap magnetomotive force (MMF). Subsequently, the flux density is calculated, which allows the calculation of no-load electromotive force (EMF) and also on-load torque. In addition, the relationship between machine performances and key dimensions can be obtained by analytical expressions without complicated finite element analysis (FEA). Analytical results are validated by both the 2-dimension FEA and experimental results.