Study Of Influence On Iron Losses Of Induction Motor Fed By PWM Inverters

In recent years, the rapid development of power electronic devices and control technologies push the speed regulation technology into a field of frequency control of motor speed. However, the AC drive technology based on PWM inverter brings some bad effects on motors. The output voltage of inverter contains plenty of harmonic components which increase the copper losses of rotor and stator and generate additional iron losses. This increases the temperature rise of motor and reduces the motor efficiency. So researching on the relationship between the modulation parameters of PWM inverter and the iron losses is an effective way to improve the system efficiency and decrease the temperature rise and motor losses.In this thesis, with the mechanism of generating motor-iron losses as a starting point, and with three-phase asynchronous motor as a study object, calculation and analysis of iron losses are completed via harmonic analysis method, time-stepping finite element method and experimental testing method respectively. The thesis also discusses the impacts on iron losses of both SPWM modulation parameters and SVPWM modulation parameters. Meaningfully, study of influences on iron losses of motor fed by SPWM and SVPWM modulation is implemented. And the research result supplies the important reference for industry applications and energy conservation.The contents can be divided into four parts. Firstly, the working principles of SPWM modulation and SVPWM modulation are analysed and the simulation model of inverters is established with Matlab to analyse the harmonic component of output voltage. It concludes the distribution patterns of harmonic waves under different modulation parameters of carrier wave ratio and modulation ratio. Secondly, based on superposition principle, the iron-loss model of motor fed by PWM supply is established to study the iron-loss variation rules under varied modulation parameters of two different modulation schemes. Then the finite element model of the induction motor is established in ANSOFT, and the motor iron losses are calculated under different carrier wave ratio and modulation ratio through time stepping finite element method. Finally, with DSP-based hardware design and software completion, the test of iron losses is finished with experimental platform and the results show that it is in accordance with the theoretical analysis.