Design And Analysis Of Brushless Electrically Excited Synchronous Machine With A Hybrid Rotor

Taking the China Natural Science Fund and the Specialized Research Fund for the Doctoral Program of Higher Education as background, a brushless electrically excitated synchronous machine(BEESM) with hybrid rotor is proposed based on reliability problems of conventional electrically excitated synchronous machines with brushes and slip rings. And BEESM is characterized with two sets of stator windings with different pole numbers. The one is three-phase symmetric winding and the other one is single-phase winding. The special structure of rotor modulates the two magnetic fields and realizes the electromechanical energy conversion. The BEESM cancels the brushes and slip rings based on the advantages of conventional electrically excitated synchronous machines, which makes the operation more reliable and can reduce maintenance costs. The systematically theoretical analysis and experimental research will be carried out on BEESM. The main research work includes the following aspects:(1) BEESM is very different from electrically excitated synchronous machine with brushes on the structure and principle. The currently available analysis theory and method are no longer applicable to BEESM. Therefore, basic electromagnetic relation and magnetic field modulation mechanism of BEESM are deeply studied. Based on the evolution course of rotor and their respective advantages and disadvantages, a new hybrid rotor is proposed which is the combination of magnetic barrier rotor and cage rotor. The equivalent circuit and electromagnetic torque expression of BEESM with magnetic barrier rotor and hybrid rotor are respectively deduced. And According to electromagnetic relationship of BEESM at different operation mode, the relationship of energy flow is deduced.(2) For the further research of coupling ability and improving the power density and running performance, the key parameters affecting the coupling capability are analyzed by using finite element method, such as pole number of excitation winding, pole arc factor, amount of magnetic layer, width ratio of magnetic and non-magnetic layer and amount of short circuit cage bar. And the optimum coupling scheme of BEESM is preliminarily determined. Based on winding function, inductance parameter calculation model of BEESM with magnetic barrier rotor and hybrid rotor is deduced and the corresponding calculation software is compiled. And the inductance parameters are quantitatively calculated and qualitatively analysed.(3) In order to systematically analysing steady and dynamic characteristics of BEESM under different operation modes, the mathematical model of BEESM with magnetic barrier rotor and hybrid rotor is deduced in the abc coordinate and the terminal voltage is presented under different operation modes. The different operating characteristics are simulated such as asynchronous starting, pulling into synchronism,synchronous operation with sudden loads, generator operation with no-loads and loads. The operating characteristics of BEESM with different poles combinations and rotor structure are comparatively analysed.(4) In view of characteristic of BEESM, air-gap magnetic field harmonic content of BEESM is relatively abundant. The copper loss and iron loss calculation models of BEESM are established, considering harmonic magnetic density, alternating magnetization and rotation magnetization. The calculated results of loss are compared with the experimental results to prove the validity of loss calculation methods. The three-dimensional temperature field calculation model is established based on calculated results of loss. And the temperature distribution of BEESM is comprehensively analyzed which provides the basis of loss analysis and temperature calculation for this kind of machine.(5) The prototypes with 6+2 poles and 8+4 poles are designed and manufactured. There are two rotor for each prototype. The one is magnetic barrier rotor and the other one is hybrid rotor. And the experimental system platform is built. The inductance parameters of prototype are measured by the static test method to verify the validity of the inductance parameter calculation model. The motor and generator operation modes of prototype are carried on the comprehensive experiment research. It proves that the proposed BEESM has good performance and further verifies the correctness and effectiveness of theoretical analysis and research method.