Design And Analysis Of Split-tooth Permanent Magnet Vernier Machine

With the quickening pace of modernization of agricultural production,the agricultural electric tractors have the advantages of energy saving,environmental protection,low maintenance cost,and low noise,which has attracted widespread attention.Due to the complex agricultural environment,as the core component of energy conversion,the machine used in its power system is required to achieve low speed and high torque output.Permanent Magnet Vernier(PMV)machine operates on the principle of magnetic field modulation and can meet the above demand.However,due to its modulation effect,to produce rich harmonics in the air-gap magnetic field,resulting in a lot of losses.And the machine adopts the fully closed structure installed in the wheel hub of the electric tractor,the heat dissipation condition is poor,which adversely affect the temperature rise and safe operation of the machine.Thereby,it has important significance in both theoretical and application terms to study how to suppress the losses and the temperature rise of the PMV machine based on maintaining the high torque output at low speed,thus ensuring the safe operation of the machine.Therefore,an outer-rotor split-tooth PMV machine is proposed in this paper.The operation principle of the machine is studied,and the influence principle of modulation teeth parameters,permanent magnet(PM)parameters and winding on the torque and the loss performance of the machine is studied.The structure parameters and winding are designed and optimized.The electromagnetic,loss,and temperature rise performance are analyzed.A prototype was manufactured for experiments.The results verity the validity of the theory analysis and the practicability of the design.The details contents are as follows:(1)A outer-rotor split-tooth PMV machine is proposed and its topology structure is analyzed.Based on the equivalent magnetic circuit method,by establishing the airgap magnetic field model,the magnetic field modulation principle of the machine is illustrated from the perspective of air-gap magnetic density harmonics.By introducing the parameters of modulation teeth into the air-gap magnetic density expression,the influence principle of the parameters on the torque performance of the PMV machine is studied.By establishing the equivalent circuit of PM and analyzing the resistance and loss of PM,the influence principle of PM parameters on the loss performance is studied.The design principle of the multi-phase winding is studied from the point of eliminating the winding magnetomotive force(MMF)harmonics by establishing the expression of the MMF of multi-phase winding.(2)Based on the operating principle of the PMV machine,by constructing the relationship between the machine dimensional parameters and the output power,the machine size is preliminarily determined.According to the design theory proposed in the previous chapter,taking the torque and loss performance of the machine as the design objectives,the structural parameters and winding of the machine are designed and optimized.The results verity the correctness of the theory analysis.The finalized machine parameters are summarized.(3)The electromagnetic performance of the machine is analyzed to verity the effectiveness of design,including the magnetic field distribution,no-load flux linkage,no-load back electromotive force(back-EMF),cogging torque,output torque,and inductance.The results show that the machine has good electromagnetic performance.(4)Study the loss performance and the temperature rise performance of the designed PMV machine.Based on the principle of heat transfer and heat conduction equation,the parameters required for the temperature simulation are calculated.Build the temperature simulation model of the machine,and the machine temperature rise is calculated by using the ANSYS Fluent simulation platform.The steady-state temperature rise distribution of the machine under rated operation is obtained.(5)A prototype was fabricated and the experimental platform was built.The noload and temperature rise performance of the PMV machine are tested.The experimental results show the no-load back-EMF of the machine matches with the simulation results.The temperature rise of the prototype under load is measured and contrasted with the simulation data,and the error is within a reasonable range.The validity of the machine design is verified through experiments.