Research On Twelve-pole Heteropolar Radial Hybrid Magnetic Bearing

Hybrid magnetic bearings(HMB)combine the advantages of active magnetic bearings and passive magnetic bearings.And it has the advantages of low magnetic leakage and low power consumption.Therefore,the above characteristics make HMB increasingly widely used in blowers,ultra-high-speed centrifuges,flywheel energy storage,artificial hearts and other fields.However,when the HMB is working normally,the bias flux and the control flux coexist,so the magnetic circuit is more complicated.At present,many traditional HMB still have problems such as large coupling and insufficient dynamic stiffness.In response to this problem,the main research content of this article is summarized as follows:(1)A twelve-pole heteropolar radial hybrid magnetic bearing(HRHMB)is proposed.And an equivalent magnetic circuit(EMC)model of the twelve-pole HRHMB is established based on the EMC method.Then the mathematical relationship of electromagnetic force-current/displacement is derived.In addition,the structural parameters of the twelve-pole HRHMB are designed with the goal of maximum bearing capacity.At the same time,through finite element simulation(FEM),the correctness of the EMC model and the rationality of the structural parameters are verified.(2)The electromagnetic field simulation analysis of the twelve-pole HRHMB was carried out using Magnet software.Then,the uniform magnetic field distribution of the twelve-pole HRHMB and the high degree of coincidence of the control flux and the bias flux are proved.At the same time,the study on the coupling between the magnetic poles of the twelve-pole HRHMB when controlling the winding current change or the rotor core displacement is carried out,and compared with the eight-pole HRHMB.The simulation results show that the twelve-pole HRHMB has the advantage of smaller coupling compared to the eight-pole HRHMB.(3)The method of Magnet-Simulink co-simulation is introduced.Through this method,the theoretical analysis,FEM analysis and control simulation analysis of the twelve-pole HRHMB can be effectively combined.Then,it is more intuitive and convenient to judge the pros and cons of the control winding current,control winding electromagnetic force,rotor core displacement,rotor core speed and other parameters of the twelve-pole HRHMB system after adding the corresponding control strategy,and compare with the eight-pole HRHMB system.The results of the Magent-Simulink cosimulation show that the twelve-pole HRHMB has lower power consumption,smaller coupling,higher structural dynamic stiffness,better suspension performance and support performance than the eight-pole HRHMB.(4)The twelve-pole HRHMB test bench was built.Then,the experimental study on the change trend and coupling of the magnetic induction in the air gap of the twelvepole HRHMB was carried out.The experiments show that the twelve-pole HRHMB is less coupled when the current changes and the rotor displacement changes.And the magnetic induction intensity-current/displacement characteristic curve in the air gap has good linearity.