Calculation And Experimental Verification For Rotor Leakage Inductance Of Unequal Coils Brushless Doubly-fed Machine

Brushless doubly-fed machine(BDFM)is a AC motor of new type,in the variable speed drive and Variable-Speed Constant-Frequency have shown a good application prospects.The stator of the brush doubly-fed machine consists of two sets of windings of two different poles.The rotor consists of a set of rotor windings.The design method of the wound rotor is flexible and reasonable,which can effectively reduce the unwanted harmonics in the rotor and lay the foundation for the practical application of the large-capacity brushless doubly-fed machine.In this paper,the principle and structure of brushless doubly-fed motor are introduced,and its mathematical model is constructed and deduced.Unequal coils,one of the sub-branches of wound-rotor coils featuring in flexible structures,can further improve the rich inclusion of magneto-motive of harmonic wave and low utilization ratio of conductor.Compared with the conventional equal coils,the structure of unequal coils can make the accurate calculation possible,both for leakage inductance of motor slot and that of harmonic wave.In order to calculate the slot leakage inductance of the rotor slot 54 six-phase double coils,this paper employs a new method(magnetic field energy combined with the number of phase coils and the incidence matrix of the direction of the electrical current)to deduce the calculation formula of the slot leakage inductance and presents the corresponding results through the analysis of the different layers of the rotor pear-shaped slot.This paper adopts the slot vector star method to calculate the distribution coefficient of the higher harmonic wave of the unequal rotor coils,short reach coefficient and coil coefficient and then deduce the formula of rotor harmonic wave.In this paper,the calculation model of the leakage inductance of rotor end is set up by the mirror method,and the formula for calculating the leakage inductance of rotor end is derived,and the corresponding calculation results are given.We build an experiment platform with a 64kW brushless doubly-fed motor as the prototype and set the power rate of side-band at 20kW and the coefficient for resistance at 0.76 to test the excitation voltage,current of the motor coils and motor efficiency.Experimental results show the correctness of magnetic field energy method for calculation of slot leakage inductance parameters.On the basis of this,the experimental results show the advantages and characteristics of winding brushless doubly-fed motor,which is carried out in no-load and on-load condition.In the end,the author summarizes the thesis and puts forward some problems to be solved.