Study On Several Key Techniques Of Permanent Magnet Synchronous Motor Supplied By Inverter

The permanent magnet synchronous motor (PMSM) supplied by inverter is being used widely with the development of the electric power and electronic technique. The design method and the application occasion of the PMSM have changed greatly because of the employment of the inverter. The inverter affects the performance of the motor. The design parameters influence the inverter and the performance of the total system likewise. So the accuracy of the motor design and the parameters calculation is required higher and higher. The motor supplied by inverter, which is not a single unit, is wanted to design and calculate according to the characteristic of the inverter.This theme comes from scientific technique plan project of Liaoning province whose series number is 20084022023. Some of the research productions are funded by the TECO-Westinghouse Motor Company. This paper researches the influence of time harmonic produced by drivers on the PMSM, explores the calculation method of the armature reactance that affects the machine's performance and calculates the partial demagnetization of the permanent magnet. At last a prototype is designed and manufactured successfully. The specific work is introduced as follow:Firstly, the influence of time harmonic on motors'performance is explored through establishing the equivalent circuit. The voltage waveform which is produced by drivers is simulated and the harmonic analysis is derived from the software Simulink. The relation between the carrier frequency and the harmonic magnitude is gained.The harmonic of the back electromotive force (EMF) is analyzed by means of the air gap relative permeance function, especially, the relative permeance function of the line-start PMSM is deduced and the harmonic equivalent circuit is built by main voltage harmonic and auxiliary EMF harmonic. The calculation method of the parameters in the equivalent circuit is found out. The computation method of the iron loss in the case of high frequency and the calculation flow of the harmonic performance are put forward subsequently. The performance variation of the motor is summed after taking time harmonic into account and the computation program is compiled.Secondly, the calculation method of the armature reactance and the current magnitude of d-axis and q-axis are researched when the cross saturation is referred. A calculation method of the armature reactance is researched when the cross saturation is referred. The influence rule of cross saturation on the armature reactance is studied through lots of computation about d and q-axis armature reactance towards to the motor having different permanent magnet structure. The reason that the armature reactance becomes large is analyzed subsequently. The merit and the demerit of the each testing method of the armature reactance are analyzed. The comparison between the calculation and the testing results is finished. Through the analysis and the deduction of the leakage reactance parameters, the calculation method of the slot leakage reactance and the harmonic leakage reactance is put forward.Thirdly, the physical process of three-phase symmetrical short circuit is analyzed and the equation of the short current is obtained. The currents of the short circuit are regarded as the space vector to analyze the characteristic of the max demagnetization Magnetic Motive Force (MMF). The process of the short circuit is simulated by transient finite element method (FEM) and the max demagnetization operating point is figured out and the result is identical to the one in analytical method. At last the factor that affects the max demagnetization operating point is explored. Altering the structure of the PM, enhancing the thickness of PM and enlarging the leakage reactance parameter are the effective method to heighten the max demagnetization operating point.Lastly, a 300rpm 6366Nm low speed and large torque PMSM phototype is designed and manufactured combined with the characteristic of inverter. The relation between the control strategy and motor structure is analyzed and the number of space MMF harmonic produced by time harmonic is investigated, from which the phase number is confirmed. Through researching the combination of pole and slot, computing the leakage flux coefficient, designing the ventilation system by means of the calculation of the temperature field and so on, the phototype is worked out. The assemble puzzle of the large power PMSM is solved through researching the manufacture technology. The phototype is manufactured successfully and the testing work is completed. Through the appraisal of expert committee the prototype reaches the international advanced level.