Electromagnetic Characteristics And Experiment Analysis Of Brushless Doubly-fed Wound-rotor Machine

Brushless doubly fed machine(BDFM)is a new type of AC motor,which is cascaded by two asynchronous motors.It has a wide application prospect in wind power generation and ship industry.The stator slot of brushless doubly fed machine has two sets of windings with different polar logarithms.The two sets of windings are indirectly coupled through the rotor.Compared with the traditional AC motor,it saves the brush and slip ring,so it has simple structure,diversified operation and good reliability.This paper studies the partial performance of wound brushless doubly fed machine.First,the development history of brushless doubly fed machine is briefly described.The basic structure and electromagnetic operation principle of brushless doubly fed machine are introduced.Several common fixed and rotor structures are compared.The electromagnetic modulation principle of the rotor is introduced.The energy flow direction of the brushless doubly fed machine is analyzed,and the steady state of the brushless doubly fed machine is derived.The mathematical model and the equivalent circuit diagram.This paper summarizes the problems of the design of the brushless doubly fed machine during the design process.The magnetic density in the air gap of the brushless doubly fed machine is analyzed,and the electromagnetic force is obtained on the basis of magnetic density.The electromagnetic force is analyzed by two bit Fourier analysis,and the harmonic content of the electromagnetic force is obtained.The influence of static eccentricity on the magnetic density of the motor is discussed.Finally,a variable speed constant frequency power generation experiment is carried out with a wound brushless doubly fed prototype.and the changes of the voltage and frequency at both ends of the motor under different loads are studied.The experimental data are compared with the theoretical analysis,and some useful conclusions are obtained.