Parameter Calculation And Simulation Research Of Pole-changing Line-start Permanent Magnet Synchronous Motor

Traditional line-start permanent magnet synchronous motors(LSPMSM) have poor start-up capability because of large braking torque and pulsating torque. A nov-el pole-changing LSPMSM is designed and made to solve this problem in this paper. At the beginning of starting up, the minor-pole windings are fed. The electri-cal source is switched to the major-pole windings at suitable moment. The novel motor almost eliminates the braking torque and pulsating torque, which improves the start-up capability. Therefore it has a promising prospect and great value of re-search. This paper presents a 30kW,380V,6/8 pole-changing motor as a research object and do the following research work:First, the method of designing phase-exchanging pole-changing windings is elaborated, and the relevant parameters of pole-changing windings and normal windings are calculated. It proves the feasibility of this start-up method by com-parison of FEA and some motor test between the novel motor and a normal motor.Secondly, with FEA and analytical method, the main reactance, leakage reac-tance and resistance of the novel motor are calculated. The method is given to calcu-late the main reactance when the numbers of poles are different between stator and rotor. When the number of poles is the same, the method of equivalent dq axis status is used to calculate d-reactance and q-reactance. Leakage reactance is calcu-lated with analytical method.Thirdly, the method of analyzing fields and the formula of calculating torques has been studied. Torque-speed curve of the two motors is calculated by the formula and parameters calculated before. It can be concluded that the EMF is almost zero when the numbers of poles are different between the stator and rotor, which im-proves the start-up capability greatly.Finally, a simulation model is established by the mathematic model of LSPMSM based on MATLAB/Simulink. Meanwhile, some special requirement of windings switching of the novel motor for the model is analyzed. Performances of the novel motor and the normal motor are compared through the simulation. It is ob-vious that the start-up torque and the time of pull-in shows the superiority of the novel motor. The controlling strategy of switching the windings has been explored and it is found that the phase difference and the speed would influence the pull-in capability. Some advice of the strategy is given by the standard of the impulse cur-rent and the time to pull-in:The most suitable moment to switch windings is the moment under the synchronous speed and the phase difference is about zero when the impulse current and the time to pulling-in are almost the least.