Single-phase Self-starting Permanent Magnet Synchronous Motor Electromagnetic Analysis

The single phase permanent magnet synchronous motor, which is of a simpler structure than that of the brushless DC motor, can self-start when sinusoidal voltage is supplied. Therefore, it has a higher efficiency than single phase induction machine. Due to its simple structure, high efficiency and low cost, the motor is a competitive household appliance in the future. Based on the motor structure and operating principle, the radial airgap flux density, the induction, the EMF and the reluctance torque are calculated, which provide a theoretical foundation to optimization design for it.Calculation of radial airgap flux density which is the base of motor design is the precondition for analyzing motor oscillation and noise. By using the magnetic circuit method, the radial airgap flux density is obtained. Since the magnetic flux distribution is difficult to calculated, an airgap relative specific permeance function is presented by means of the Schwarz-Christoffel transformation, and the distribution of stator port flux density is calculated. In addition, for two operating cases related to the stator current waveform and permanent rotor axis position, a two-dimensional finite element method (2D FEM) is used to analyze the magnetic field of the motor. Magnetic lines of flux and air-gap radial flux density waveforms at four typical patterns are obtained.Magnetic lines of flux and radial airgap flux density waveforms at three typical conditions are obtained by 2D FEM. Magnetomotive is resolved into the d-axes and q-axes by using double-reaction theory. The principle of superposition is utilized to deduce flux density waveforms with stator winding excited. Consequently, the radial airgap radial flux density waveforms can be gained accurately and conveniently with rotor in the arbitrary position and stator winding excited by any current.The stator winding inductance, EMF and reluctance torque calculation are carried out by two different methods, the magnetic circuit method and FEM. The agreement between the experiment results and the calculation results validates the reliability and accuracy of the analysis methods presented.