Discussion Of The Mechanism Of The New Three-phase Capacitor Motor And Its Speed

The energy-saving technologies for electric motor drive systems are receiving increasing attentions from governments of nearly all nations. Thanks to the success in a specially designed winding structure, the three-phase capacitor motor is an energy efficient one with high power factor. Based on comprehensive analysis and research on the mechanism of this new type of novel three-phase capacitor motors, the excellent performances of the motor such as high power factor, elimination of the space magnetic harmonics, and high efficiency are confirmed positively. Meanwhile, the speed regulation strategy for the potential applications of the machines is also studied with the goal of maximizing the energy efficiency without satisfying the general performance parameters.The paper is organized as follows:The first chapter is the introduction, summarizing mainly the background of the research and the concept of three-phase capacitor motors.The second chapter is focused on the study of the harmonics of the air gap magnetic fields. The main concern is placed on the fundamental, the 5^th, and 7^th harmonic components of the three-phase capacitor motor in symmetrical operation conditions. The mathematical model of the machine is derived based on a double rotating magnetic field theory. The numerical results obtained from the model show good agreement with the tested ones.Chapter three is a continuation of the work of the previous chapter. A more accurate mathematical model of the machine is developed by considering further the 5^th, 7^th, 11^th and 13^th harmonics components of the air gap magnetic fields. This model can be used to determine harmonics ripples of the electromagnetic torques.To facilitate debugging and simulation to short the developing period, Chapter four is dedicated to the study of the dynamic model of the three-phase capacitor motor. For this purpose, the d-q reference model is developed. The dynamic performance of the machine is investigated by using Matlab/Simulink.Based on the mechanism of the 5^th and 7^th harmonics weakening of the air gap magnetic field, Chapter five proposes an energy saving variable frequency control strategy by using the difference between the main winding current and the co-winding current phases as an auxiliary control objective. The proposed speed control strategy is numerical studied by using Matlab/Simulink. Analysis of the relevant engineering issues is also included.