Analytical Calculation of Air-Gap Magnetic Field of the Trapezoidal Surface Permanent Magnet Machine

Based on the magnetic field which is excited by a pair of windings on the air-gap, the calculating formulas of the air-gap flux density excited by parallel-magnetized permanent magnet with different shapes are deduced with surface current method. The results show that the air-gap flux density excited by permanent magnet with different circle and radius is trapeziform wave if the size of permanent magnet properly chosen. Comparing the analytical method with 2D finite-element method and comparing the BEMF result got from the analytical method with the result of experiment, it is proved that the proposed method is reliable. The proposed formulary can be of great help tithe optimizing design and performance analysis of permanent magnet synchronous motors.