Research And Design Of High-capacity Excitation Compensation Type Doubly-fed Start-up Low-speed PMSM

With the proposed concepts of “Made in China” and “The Pillars of a Great Power”,there are higher requirements of energy saving and environment-friendly in industrial fields such as port crane,building machinery,petroleum and mine.Low-speed high-torque PMSM can effectively cancel the traditional variable-speed link and has become a hot spot in the field of equipment manufacturing.This paper studies the mechanism of auxiliary excitation compensation of large PMSM start-up process,uses parallel magnetic circuit structure to fit for weak magnetism,and puts forward the DC auxiliary exciting windings in the lower region of the rotor slots to realize the compensation of permanent magnetic field.Depending on the spatial arrangement of the auxiliary windings,during the start-up phase,this new structure of motor rotor windings which applying to DC exciting currents will form the MMF contrary to the permanent magnetic field,to achieve an effect that Weakening permanent magnetic field,and improving the motor starting ability fundamentally.Depending on the auxiliary excitation compensation theory and according to the actual demands of the building machinery project,a 33r/min,2000 kW high-capacity doubly-fed start-up low-speed high-torque PMSM is designed.This motor uses the electric power supply with power frequency and the DC excitation of the auxiliary windings to achieve the doubly-fed start-up,thus eliminating the large capacity variable frequency speed regulating device,which is favorable for reducing the cost of the driving system.Firstly,a preliminary motor design based on the magnetic circuit method is completed,this paper analyzes the effects on the comprehensive motor performance which armature conductors per slot,core length,permanent magnet sizes(width,thickness),rotor slot sizes(slot opening,slot breadth,slot depth)and other key parameters do based on parametric software,and optimizes the motor design scheme.Then using the finite element software to built up and simulate the finite element model.While using the auxiliary excitation compensation,the no-load air gap magnetic field distribution and the rated operating state are analyzed,the simulation of the excitation compensation type doubly-fed start-up is carried out,the demagnetization point is checked and the loss analysis is completed.The motor design scheme is adjusted to optimize the machinecomprehensive performance according to the analysis results.By the analysis of the analytic calculation and simulation,the proposed high-capacity excitation compensation type doubly-fed start-up low-speed PMSM has a significantly improved starting ability,higher efficiency,lower costs,laid a theoretical foundation for the research and design of a new type of large capacity motor,for the development of lifting equipment has opened up new ideas.