Research On Axial Flux Switched Reluctance Motor With Grain Oriented Electrical Steel

As a component of energy conversion in drive system,switched reluctance motors(SRMs)have several advantages such as rugged construction,low cost,fault tolerance capability and high starting torque.However,compared with permanent magnet synchronous motor,low torque density restricts the SRM in widely used.Theoretical analysis and optimization design are carried out in this thesis to improve the axial flux switched reluctance motor(AFSRM)torque density and reduce the iron loss.Research results are verified through the prototype experiments,the main research work and achievements can be summarized as the following aspects:1.The basic characteristics of common ferromagnetic materials used in electrical machine are compared and analyzed.According to the structural characteristics of the AFSRM,a modular structure method is proposed to optimize electromagnetic conversion capability of the AFSRM by employing the grain oriented electrical steel(GOES)’s excellent magnetic properties in the rolling direction.2.Various stator structures are introduced to improve the utilization of the rolling direction in GOES,such as the length reduction of flux path running in GOES along the rolling direction and ameliorating magnetic field distribution at the junction part of the stator teeth and yoke.The feasibility of the GOES used in the AFSRM is proved.3.According to the various characteristics of the stator and rotor teeth of the AFSRM in different circle radius,combining electromagnetic characteristics of iron core material,the quasi three dimensional magnetic circuit method is used to present a preliminary design scheme.Based on the analysis of quasi-three dimensional magnetic circuit method,quasi-three dimensional finite element analysis(FEA)is used to optimize the major design parameters in different material used model,such as rotor diameter ratio,stator pole arc,axial length of the stator yoke and rotor pole arc.The analysis results show that the electromagnetic performance of the AFSRM based on the GOES is significantly better than that of the motor using traditional material.4.The electromagnetic loss results are used as the heat source of thermal model to determine the operating temperature of the motor under different working conditions.Further set mechanical parameters of the epoxy resin laminate(ERL)used in rotor retaining ring under specific temperature condition.Simplified Taguchi method and mechanical FEA are used to analysis the Mises stress and deformation caused by unbalanced axial magnetic force under different fault conditions.The analysis results are used to obtain the structure optimization parameters on the premise of meeting the electromagnetic performances.5.According to the GOES material properties and control characteristics of switched reluctance motor,rolling direction optimization strategy of GOES used in stator and rotor teeth is proposed to improve the performance of the motor.Research results show that the average torque and iron loss of the motor under certain optimized angle condition are superior to the performance obtained by original motor which the rolling direction is perpendicular to the motor axial direction.6.Static and steady-state parameters integrated test platform for AFSRM is built to verify the design and optimization results.The static flux linkage of the prototype at different rotor position is measured and compared with the FEA results.The reason of the error is analyzed,and experiments are conducted to validate the calculated data.In steady state parameters testing experiments,average torque and efficiency of the motor under different conduction angles and load conditions are compared and analyzed.Temperature rise distributions of the prototype under different load conditions are measured by infrared camera.Measurement results improve the reliability of ERL used in AFSRM’S rotor retaining disk.