The Finite Element Analysis On Performance Of Variable Freqrence Motor At No-Load And Starting

Variable frequency and variable speed motor system is of high intelligence, high reliability, fault-tolerant capability. With country economy increasing, electric and electronic technology advancing rapidly, variable frequency motor begins to apply in such industry as machine tool, metallurgy, electric power, pulling, chemical industry, textile industry, water supply, paper making, building material, agriculture, and so on, and it is much evidently energy-saving. In 1990s, people research variable frequency and variable speed system mainly on topological structure and control algorithm, which make dynamic performance and the precision of variable speed highly improved. But such performance of motor as efficiency, power factor and power density don't be emphasized and studied. So it is necessary to consider again the design of motor in variable frequency and variable speed system. Based on much merit and demands of country economic construction, theoretic research is carried on the aspect.In this paper, firstly the mathematic model for variable frequency motor is developed, and harmonic wave is analyzed when variable frequency motor is fed by inversion. Secondly, the solved region, boundary condition and hypothesis condition of the electromagnetic field in electric machine are given. In virtue of variation theory, boundary problem of magnetic field is changed into equivalent variable problem. Then the procedure of element analysis, discrete format and collective composition equation in sinusoidal and time-varying field are given. In the process of numerical calculation of electromagnetic field, stator ending voltage is taken as constraint condition and stator current under load is iterated, then no-load and starting current at rated voltage is obtained. Finally, by comparing calculated results in sinusoidal electromagnetic field with testing results, we find that the calculation results of no-load performance for variable frequency motor is accord with testing results, and calculated results of starting performance meet the demand with project practice, which proves reliable to use FEM to analyze sinusoidal electromagnetic field of motor.