Loss Characteristic Investigation Of Induction Motors Under The Situation Of Harmonic Power Supply

With the wide application in power grid of electronic devices, reactive power compensation device and inverter, terminal supplied voltage of electrical motor in harmonic content becomes increasingly outstanding issue. In view of the harmonic problem of terminal supplied voltage of electrical motor, this thesis systematically study the influence factors of loss of induction motor under variable frequency power supply and power supply contains harmonic two kinds of non-sinusoidal power supply situation with the method of theoretical analysis, simulation computation and experimental study, the main works are as below.1. According to the traditional selection method of simulation step, this thesis presents a method to determine the time-step finite element simulation step through carrier frequency. The results show that, the proposed simulation step selection method can consider the effect of the inverter output voltage harmonics of loss calculation, and reasonable shorten the calculation time of simulation.2. Traditional inverter fed induction motor iron loss calculation methods are considered from the whole. The stator and rotor core in different parts of magnetic flux density waveforms, the iron loss varies with carrier frequency and modulation ratio are analyzed in detail in this paper. The study found that carrier frequency has the most obvious effect on tooth top position of stator and rotor core. The harmonic loss of the typical position of tooth top change markedly, and the yoke of stator and rotor have less affected by harmonic. Compared to the carrier frequency, the modulation ratio increases, the core loss and copper loss of asynchronous motor decrease obviously.3. According to the harmonic pollution situation of the grid, the simulation and experiments are done by a programmable power supply. The air-gap flux density, flux density of the iron core, current density of rotor bar and changes of the loss of motor are analyzed. Analysis showed that the power supply consists of 5th,7th,11th and 13th harmonics. With the increase of harmonic content, the iron loss of motor varies a little, but copper loss and total loss increase obviously.