| Characterized by simple structure, high reliability, low noise, small vibration as well as easy maintenance, single-phase motors, operating at single-phase AC power supply, are widely used in industry, agriculture, transportation and household appliances, etc. From the view of the world, there is a huge demand for single-phase motor. In the developed countries, the output of the single-phase motor is about ten billions every year. In China, due to the need of the development of industry and agriculture, the single-phase motor output continuously increases in recent years. Therefore, it will have very important economic significance and social value to improve the efficiency of single-phase motors.However, in comparison with single-phase motor with the same capacity, the three-phase induction motor has the advantage of higher material utilization and higher efficiency, and the three-phase permanent magnet synchronous motor (PMSM) has the characteristics of high power density, high efficiency as well as high power factor and so on. Taking these advantages into account, running a three-phase motor on a single-phase supply with the help of phase balancers could be a simple and effective method to raise single-phase induction motor efficiency. So, this paper is carried out on connection method of the single-phase motor with three stator windings.In the first chapter of the thesis, research background of single-phase induction motor and single-phase permanent magnet synchronous motor is reviewed. Especially, the research status of the single-phase induction motor and single-phase PMSM with three windings are introduced.In the second chapter, a novel connection mothed with three parallel-connected windings is proposed, and which is applied on the three-phase induction motor operating under the single-phase supply. By the way of theoretical analysis, simulation analysis and experimental investigation, the analysis of the single-phase induction motor with three parallel-connected windings is carried out, and the main contents are as follows:(1) Based on the synthesizing currents method, the condition for the balanced operation is analyzed and the corresponding relationship of matched capacitances and slip ratio is also obtained. Then, the approach for calculating the steady-state performance is proposed, providing a theoretical basis for determining required capacitances and steady-state performance analysis.(2) In the ABC coordinate system, the transient mathematical model of the single-phase induction motor with three parallel-connected windings is established, and the simulation model is constructed by MATLAB/Simulink. Then two starting methods are studied, the one is with double starting capacitors in the starting circuit, and the other is only one starting capacitor. The results demonstrate that the starting torque is larger and the startup is faster by the starting method with double starting capacitors, but by starting method with one starting capacitor it can simplify the starting circuit and achieve cost saving.(3) In order to verify the feasibility of the matched capacitors and the validity of the performance analysis method, a three-phase induction motor (Y100L1-4) is chosen as the prototype, which is reconnected according to the proposed connection and supplied from a220V/50Hz single-phase supply, and the steady and transient experiments are carried out. The steady experiments indicate that, in comparison with three-phase induction motors of the same capacity, the novel single-phase induction motor has approximately the same efficiency but higher power factor when operating at rated load. The transient experiments prove that the starting time of the prototype is almost the same no matter it is supplied by a three-phase balanced voltage or by a single-phase voltage.The single-phase LSPMSM with three parallel-connected windings is fully researched in the third chapter, and the main contents can be stated as follows:(1) Based on the symmetrical component method, the condition for balanced operation is analyzed and the relations between matched capacitances and positive-sequence impedance are also obtained. The sequence impedances for synchronous operation and for starting are given in this paper, respectively, which are different for different operating states.(2) The steady-state performance analysis method is put forward based on the symmetrical component method. In order to verify the correctness of the performance analysis, two1.5kW,220V/50Hz,4-pole, Y-connected three-phase LSPMSMs, one with power factor only0.80and the other with higher power factor0.99, are designed as prototype motors, and the steady-state performance tests are carried out. It is proved that three-phase LSPMSM with lower power factor is more suitable for being reconnected to operate from a single-phase supply, improving the power factor and saving permanent magnetic material.(3) In the dqO coordinate system, the transient mathematical model of the single-phase LSPMSM with three parallel-connected windings is established, and the simulation model is constructed by MATLAB/Simulink. In order to verify the validity of the above simulation model and study further the transient performances of the proposed single-phase LSPMSM, some experiments are made on the prototype motor with lower power factor. The experimental results show that the single-phase LSPMSM with three parallel-connected windings has good starting performances.The single-phase LSPMSM with series connection and SEMIHEX connection are studied in the the fourth and fifth chapters, respectively. At first, based on the symmetrical component method, the condition for balanced operation is analyzed and the approach for calculating the steady-state performance is proposed. Secondly, based on MATLAB/Simulink, the simulation model is constructed and the simulation researches are carried out. Thirdly, two1.5kW,4-pole, Y-connected three-phase LSPMSMs, one with rated voltage190V and the other with rated voltage220V, are designed as prototype motors, and the steady and transient performance tests are carried out. It is demonstrated that good steady and transient performances can be achieved by selecting suitable capacitors, the theoretical analysis is correct.In the sixth chapter, two general problems of the single-phase motors with three windings including the single-phase induction motor with three parallel-connected windings, the single-phase LSPMSM with three parallel-connected windings, the single-phase LSPMSM with three series-connected windings and the single-phase LSPMSM with SEMIHEX connection are studied. Firstly, the running capacitors of the single-phase motors with three windings are optimized based on genetic algorithm. Taking the single-phase LSPMSM with three parallel-connected windings and lower power factor for example, the optiminal results are verified by simulation. Secondly, the reasons for the harmonic current of single-phase LSPMSM with three windings and single-phase induction motor with three windings are analyzed. Based on Ansoft Maxwell2D, the field-circuit coupling time-stepping finite element analysis is carried out, and the proposed harmonic generation theory is verified. |
