Analyze And Design On Torque Stability Of Magnetic Gears

Field modulated magnet gear is a kind of contact-free transmission device.The harmonics generated by the permanent magnets of its internal and external rotors realize the transfer torque through the magnetic field modulation effect of the magnetic field modulated ring.Field modulated magnet gear effectively avoids the problems of friction,noise,lubrication and so on brought by mechanical gear,which has been paid more and more attention in industrial production.In this paper,the torque stability of magnetic gear is enhanced by improving the structure of magnetic gear.The transmission stability of magnetic gear is promoted by increasing the output torque and reducing the torque ripple,on the premise of the same size and amount of permanent magnet.Firstly,this paper introduces the topological structure and working principle of magnetic gear,and analyzes the air gap flux density when the internal and external permanent magnets of the rotor are acting alone.Then the air gap flux density was calculated by the superposition theorem when the internal and external permanent magnets of the rotor work together.Besides,the magnetic field modulation was analyzed in detail by introducing a magnetic ring.Finally,a two-dimensional model is established by finite element method,and the air gap flux density and output torque of magnetic gear are obtained through simulation.The correctness of the principle analysis is verified.The concept of damping system in synchronous generator is introduced into magnetic gear in this paper,and a magnetic gear structure with metal sheet is proposed.A layer of conductive and non-magnetic metal material is fixed on the outer and inner sides of the permanent magnet of the rotor,in this topology.An improved magnetic gear model is established via the finite element method,the inner and outer air gap magnetic field and torque of the magnetic gear are calculated by simulation.The harmonics of air gap flux density and torque ripple are analyzed in detail.The results show that the magnetic gear containing metal layer can not only reduce the high order harmonics of air gap flux density,but also reduce the torque ripple.Halbach array magnetization can strengthen the magnetic field on one side and suppress the magnetic field on the other side.The application of Halbach array magnetization can enhance the air gap flux density on the air gap side of the magnetic gear,so as to improve the output torque.Therefore,a magnetic gear device with non-uniform air gap and Halbach array is presented in this research.The permanent magnet of the inner rotor is a sinusoidal magnetization of non-uniform segments,while the outer rotor is a simplified Halbach array.A two-dimensional model is established by finite element method,and the output torque of magnetic gear are obtained.The results illustrated that this structure of the magnetic gear can increase the output torque of the magnetic gear,so the stability of the magnetic gear is ameliorated.A superconducting modulated magnetic gear is proposed to handle the magnetic flux leakage problem.Both the inner and outer rotor permanent magnets are magnetized by Halbach array with local magnetic effect.The magnetic tuning ring is composed of magnetic modulated block and HTS(high-temperature superconducting)material alternately.High temperature superconducting material has the effect of absolute magnetic field at the critical temperature,reducing the magnetic leakage in the magnetic modulation ring and improving the utilization ratio of permanent magnet.Using the finite element method to build a two-dimensional model,the magnetic line distribution and output torque of the magnetic gear are obtained.By comparison,it is found that the magnetic gear structure reduces the magnetic leakage and improves the output torque,so the stability of the magnetic gear is enhanced.