Research On The Key Technology Of Brushless Doubly-Fed Machine With Hybrid Rotor Of Reluctance And Short Circuit Winding

Brushless doubly-fed machine (BDFM) is a special structure AC machine. In stator, there are two sets of three-phase symmetrical windings with different pole pair. Rotor is divided into cage and reluctance structure. BDFM has the advantage of simple structure,reliable operation,fine governing characteristic,small converter capacity,it has good prospect in frequency control system and wind power. But the weak coupling capability and rich harmonic magnetic field of conventional rotor cause that BDFM has low efficiency and power density, its promotion and application are affected. In this paper, the following study is been done to improve the coupling capability of rotor.Firstly, the coupling capability of different conventional reluctance rotor is investigated. The salient pole reluctance rotor is the most traditional rotor, this paper studies the effect discipline of pole-arc factor and salient pole height on the coupling capability of rotor. The reluctance rotor with magnetic obstacle is formed by increasing magnetic obstacle in salient pole reluctance rotor, and study the effect extent of different magnetic obstacle length,width and number on the coupling capability of rotor. In order to improve the coupling capability of rotor further, hybrid rotor with short-circuit ring and reluctance is designed by filling with short-circuit conductor in the reluctance rotor with magnetic obstacle. Analysis the coupling capability of the three rotors quantitatively.Secondly, the coupling capability of ALA rotor is strong,but it uses the form of axially laminated,rotor will produce lager eddy current when the motor is running, resulting in the low efficiency. So,this paper studies a radially laminated rotor with magnetic obstacle. Using the finite element method to analysis the effect of pole-arc factor, conducting magnetic width,number and the width radio of conducting magnetic and magnetic obstacle layer on the coupling capability of rotor. In addition, increase the short-circuit conductor in the magnetic obstacle layer, and analysis the coupling capability of radially laminated hybrid rotor quantitatively.Then, inductance and loss are two important parameter, they are directly impact on the performance of motor. As the complex structure of BDFM, this paper selects the energy perturbation method to calculate the inductance parameter of reluctance rotor with magnetic obstacle BDFM, compares the inductance parameter with short-circuit ring and without short-circuit ring. In addition, calculate the loss of motor with the finite element method.Finally, according to the previous findings, a BDFM is designed, and power is 200kW. The fundamental size of motor is same as the size of Y355 asynchronous motor, the two windings are double short-rang distributed winding, determine the hybrid rotor structure with short-circuit ring and reluctance. The calculation of the coupling capability and characteristic simulation under doubly-fed are carried out.