Study On Parameter Calculation And Control Strategy Of The Pole-changing Line-start Permanent Magnet Synchronous Motor

In recent years, with the rapid development of social economy, human need more and more energy to support their development. Human’s consumption on energy is increasing highly, while energy reserves are getting smaller and smaller. Saving energy, reducing consumption and improving energy efficiency are very important ways to solve this problem. Motor system accounts for 60% of the country’s total electricity consumption every year. Energy-saving potential is large. It is the main target of electrical energy consumption. But energy-efficient motors account for only 10% of the market at present in our country. To improve the efficiency of the motor can save a lot of energy. Therefore it is imperative to research and design efficient motor! Line-start permanent magnet synchronous motor is of high efficiency. It achieves prominent economic efficiency and social benefits in the productive application.However, the starting capability of line-start permanent magnet synchronous motor is poor. To solve this problem fundamentally, this paper studies the new type of pole-changing line-start permanent magnet synchronous motor. The main work is as follows:(1) The working principle of the line-start permanent magnet synchronous motor and the pole-changing line-start permanent magnet synchronous motor were analyzed. Then two-dimensional finite element models of line-start permanent magnet synchronous motor based on the new type of 6/8 pole-changing windings and ordinary line-start permanent magnet synchronous motor were established. FEM analysis was used to analysis two motors. No-load counter electromotive force, braking torque, torque ripple and average torque of two motors were compared. We can conclude that the starting capability of the pole-changing line-start permanent magnet synchronous motor is higher than the ordinary line-start permanent magnet synchronous motor.(2) Inductance parameters of pole changing winding were calculated by means of analytical method according to magnetic permeance analysis method and multi loop theory. Then the inductance parameters of pole changing winding were calculated by finite element method to verify the correctness of the result of analytical method. At first, the Inductance parameters of stator loops were analyzed. Then the inductance parameters of rotor loops were analyzed. At last, the mutual-inductance parameters between stator loops and rotor loops were analyzed.(3) Simplorer 11 and Maxwell 16 were used to study the best time to switch the windings. Firstly windings were switched at synchronous speed and speed higher than the synchronous speed. In order to remove the extra speed measuring equipment, control circuit of the motor was improved. Induced electromotive force of 8-pole windings is rectified and wave-filtered to get a dc voltage. The dc voltage is used to detect the motor speed. Windings are switched according to the dc voltage. At last simulation analysis was accomplished according to the improved control circuit.(4) Experimental research. No-load counter electromotive force of 6-pole winding and 8-pole winding at different speed of the motor are compared. Then the motor was started with the 6-pole winding and 8-pole winding respectively. The threshold voltage and the loudness of noise of motor starting were acquired.