Electromagnetic Performance Analysis Of Multiphase Induction Motor With Pole Changing

Multiphase induction motors is easy to achieve large power in the low voltage situation, good fault-tolerance capability, the multiple control freedoms, small fluctuation of the torque. Multiphase electronic pole changing induction motors integrate the advantages of multiphase induction motors with the technology of electronic pole changing. So multiphase electronic pole changing induction motors not only have the numerous advantages of multiphase induction motor, but can realize wider speed regulation range without power cut. They are more even comprehensive applied to ship propulsion, electrical traction and electric aircraft applications. The thesis mainly studied the following aspects:structure of the motor and the stator windings and the electromagnetic performance when the motor operates in different pole phase situations.Firstly, mathematic models of multiphase induction motors are built by using the method of space decomposition. And through analyzing mathematic models of the motor under the nature base and harmonic base, the motor’s physical nature which is that motor’s magnetic field is constructed by the structure of the windings and the excitation of the motor is proved. Through analyzing the multiple control freedoms of the multiphase motor, it can be found that the multiple control freedoms can realize pole changing speed regulation.Then, regarding a 30kW multiphase electronic pole changing induction motor as the object of the research, the structure of the windings is designed detailedly. Through researching the current distribution of stator windings when the multiphase electronic pole changing induction motor operates in five pole phase situations (48-phase 2-pole, 24-phase 4-pole,16-phase 6-pole,12-phase 8-pole and 8-phase 12-pole), the motor can realize electronic pole changing. By using winding function theory, space-time harmonic distribution of the motor and its impact on the electromagnetic performance of the motor is analyzed.Finally, the motor’s 2D finite element model built by Maxwell soft is used to compute the flux density, electromagnetic torque and efficiency when the motor operates in five pole phase situations excited by fundamental current source. Then, by injecting 3rd time harmonic in the motor’s excitation, the torque density and power density of the motor can be improved.