Instantaneous magnetic field distribution in brushless permanent magnet DC motors. I. Open-circuit field

Abstract

An analytical technique for predicting the instantaneous magnetic field distribution in the airgap region of radial-field topologies of brushless permanent magnet dc motors, under any specified load condition and accounting implicitly for the stator winding current waveform and the effect of stator slot-openings, has been developed. It is based on the superposition of the component fields due to the permanent magnet and the stator excitation. In this paper, which is one of a series of four, a 2-d analytical method for predicting the opencircuit airgap field distribution in both internal and external rotor radial-field motor topologies is presented. It involves the solution of the governing field equations in polar coordinates in the annular airgaplmagnet region of a multi-pole slotless motor in which the magnets are assumed to have uniform radial magnetization and a constant relative recoil permeability. Results for various radial-field motors are compared with predictions from corresponding finite element analyses.

Improved Cogging Calculation Methods for Surface Mounted Permanent Magnet Synchronous Motors

“…The well known cogging torque formulae of Zhu and Howe is in common use [1] [2] [3] and is used in this study. It is formulated in three stages.…”

Analytical Calculation of Magnetic Field Distribution and Stator Iron Losses for Surface-Mounted Permanent Magnet Synchronous Machines

“…Alternatively, an analytical calculation method can commonly be used to obtain solutions expressed in the form of a Fourier series which is flexible as a design tool for predicting the losses and motor performance [14]. Some analytical methods have been proposed to determine the magnetic field distribution of PM machines [15][16][17][18][19]. An exact field solution in the air gap of an SPM motor with radial or parallel magnetization was given in [15,16].…”

Semi-Analytical Model for Skewed Magnet Axial Flux Machine

“…Furthermore, computational complexity and inaccuracy are high especially for irregular shape of machine's geometry and magnetic saturation. In 1993 Zhu et al [13] solved magnetic field distribution in a slotless permanent magnetic machine by use of variable separable method. Further, the authors incorporated the slotting effect using conformal mapping approach and deducted a 2D relative permeance function to account for the slotting effect [6].…”