Design And Optimization Of A New Type Of Synchronous Reluctance Machine

Due to the high price of rare earth permanent magnet,synchronous reluctance machine(Syn RM)has been paid more and more attention.As the stator of Syn RM has no permanent magnet,its stator is the same as that of traditional induction machine,and as well because the rotor of Syn RM is designed with multi-layer magnetic barriers,the high saliency ratio and the reluctance torque can be produced.The Syn RM has the advantages of simple structure,low loss,good mechanical robust and low cost.However,the rotor of the Syn RM has no excitation source,which requires the stator armature winding to generate excitation components to form the magnetic field that needed for the operation of the machine.So the torque and power factor of the Syn RM are low.At the same time,the silicon steel sheet at the key position of flux flow such as rotor magnetic bridge and stator teeth of Syn RM will be saturated under the overload operation,which will increase the heat of the machine and reduce the output torque.To solve the problem of magnetic circuit saturation of Syn RM during overload operation,a new type of synchronous reluctance machine(NSyn RM)is proposed in this paper.Compared with traditional Syn RM,the rotor magnetic bridge and stator teeth of NSyn RM are embedded with oriented silicon steel to make the rolling direction of oriented silicon steel flow along the d-axis magnetic field.Obviously,the non-oriented silicon steel in the magnetic circuit of the machine is easy to reach saturation under overload.However,with the characteristics of high permeability and high saturation magnetic density in the rolling direction among the oriented silicon steel,the flux can flow smoothly along the oriented silicon steel,from which the anti-saturation ability of the machine and the output torque are improved.Then the low-price ferrite is added to the rotor magnetic barrier to form a new type of permanent magnet-assisted synchronous reluctance machine(PM-NSyn RM)based on the NSyn RM to further improve the output torque.And the permanent magnet magnetic field is generated by ferrite and coupled with the d-axis component of the armature winding to produce permanent magnet torque.In the case of overload,the machine has a certain anti-saturation ability and the output torque is greatly increased,but because the demagnetization of ferrite is considered,the maximum overload current applied by the machine is less than that of the Syn RM.Firstly,the operation principle of Syn RM is introduced and the mathematical expressions of voltage,flux linkage,torque,inductance and other parameters are listed in this paper,which provides a theoretical basis for follow-up machine structure optimization and performance analysis.Then using the finite element software Maxwell,the influence of the main structural parameters on the performance of the Syn RM and the NSyn RM proposed in this paper are analyzed,such as split ratio,stator tooth width,insulation ratio,edge magnetic rib,magnetic barrier angle.On the basis of the two kinds of machines,the output torque、power factor and efficiency of the two machines under the rated current density and the maximum current density are compared and analyzed.Besides,in order to further improve the output torque of the machine,the PM-Syn RM is introduced,its mathematical model and torque composition are listed,and the demagnetization area of ferrite is analyzed under different current density.Finally,the torque of the four machines proposed above are compared under different current densities.Through the research and analysis in this paper,some ideas are provided for the future design of synchronous reluctance machine.