Research On A Brushless Claw Pole Double Rotor Machine Used For Hybrid Electric Vehicles

Compound-Structure permanent-magnet synchronous machine (CS-PMSM)developed recently is a novel type of machine, which is composed of two electricmachines. As the critical component in the hybrid drive system, it is able to improvethe fuel economy and reduce the exhuast emission of the veichle by harmonizing theenergy distribution between the internal combustion engine (ICE) and the battery.So far, the research on CS-PMSMs with brushes all over the world is becomingmature. The effictiveness and the advantage of the CS-PMSM have been verified bythe current achievement. However, the research also shows that there areunavoidable problems in the scheme with bushes, such as the severe heating of thewindings of the inner rotor and the reliablity of the bushes. In this paper, a novelBrushless Claw Pole Double Rotor Machine (BCDRM) is proposed. The BCDRM isable to cooperate with traditional machines of different structures to realize thefunctions of the CS-PMSM. And it can achieve the independent control of the torqueand the speed of the ICE respectively. Moreover, it solves heating of the windings ofthe inner rotor and the reliablity of the bushes, which have been perennial problemsin the CS-PMSM. The research of this paper mainly consists of the following parts:Firstly, the distribution of the main magnetic flux and the magnetic fluxleakage in BCDRM is investigated. The equivalent magnetic circuit model isestablished according to the characiteristics of the magnetic circuit of BCDRM.Furthermore, taking advantage of the proposed model, the reluctance of the model iscaculated, and analytical formulas of the torque and reactance are deduced.Secondly, three-dimension (3-D) FEM is utilized to obtain the distribution ofmagnetic flux denstiy in the airgap, and caculate the no-load back electromotiveforce (EMF), the flux leakage coefficiency under no-load condition and thereactance of the BCDRM. The BCDRM is characterized by high leakage flux andcomplex flux paths. Therefore, the magnetic flux leakage of the BCDRM isanalyzed and caculated, and the errors introduced by the approximate caculation inthe analytical formulas of the reluctance in the equivalent magnetic circuit model arecompensated. Additionally, the2-D FEM model of the BCDRM applying toengineering applications is bulit so that the model complexity and time-consumingin the3-D field calculation can be avoided. An entire practical design procedure forBCDRM is proposed in this paper, which greatly facilitates the design of theBCDRM.Thirdly, the expressions of torque density and cogging torque of BCDRM arededuced by analytical method. The effects of the dimension parameters on the torque density and cogging torque are discussed and evaluated. Then3D FEM isused to analyze the the torque characteristics of the BCDRM, the configuration ofthe PM rotor, pole-pair number, air-gap length, ratio of the main dimensions andclaw-pole shape are optimized and the optimal structure with the best torqueperformance was obtained.Afterwards, studies show that the power factor of BCDRM is low and thisshortcoming is caused by the serious flux leakage. The influence of permanentmagnets, number of winding turns, amplitude and phase angle of currents on thepower factor of BCDRM are studied and the approach to obtain higher power factoris given. In addition, the core loss of the claw poles using silicon steel sheets, SMCand solid iron block was compared, and and hereby making the silicon steel sheetsas the final selection. Through calculation, the proportion of each kind of loss in theBCDRM is got and the efficiency of BCDRM is evaluated.Lastly, a prototype machine of the BCDRM is manufactured, and theexperimental test was designed to perform its functional validation. The accuracyand feasiblity of analytical and electromagnetic caculation is validated bycomparisons between the measured results and the caculated ones, including no-loadback-EMF, cogging torque, reactance and so on. Moreover, the operating mode ofthe BCDRM in the hybrid system is simulated based on the constructedexperimental platform. The experimental results verify the speed adjustmentfunction of the BCDRM, and these lay the theoretical and technical foundations forthe practical application of the BCDRM in hybrid veichles in the future.