Research On Short Circuit Of Three-phase Modular Permanent Magnet In-wheel Motor

Permanent magnet synchronous hub motors are increasingly used in special vehicles due to their high speed and high torque.Special vehicles have a harsh working enviroN·ment,and various faults may occur during the operation of the hub motor.Among the various types of faults,there are various types of short-circuit faults,which are serious.When the motor is short-circuited,the lighter hazard is caused by large torque fluctuations,local temperature rise and severe vibration.The most dangerous situation is to burn the motor or even the entire motor drive system.Cutting off the fault phase or even the faulty power supply module cannot solve the problem fundamentally.How to accurately detect the occurrence of faults and how to design the motor to have a certain short-circuit fault tolerance is a research hotspot in the current motor field.In this paper,the short-circuit current,torque performance,electromagnetic force wave and vibration characteristics of the motor short-circuit fault are studied,and a modular in-wheel motor scheme is proposed.The main work includes the following aspects:Firstly,the short-circuit current and torque performance of the motor under fault conditions are analyzed for the types of short-circuit faults that may occur in the motor,including the end short-circuit fault and the turn-to-turn short-circuit fault.For the inter-turn short circuit fault,establish a turn-to-turn short circuit fault model.The changes of short-circuit current and torque performance under the inter-turn short circuit fault are analyzed from three aspects: contact resistance,position of short circuit and number of short circuit.Secondly,based on the electromagnetic force analysis process under the normal running state of the motor,the expression of the electromagnetic force under the single-phase end short-circuit fault of the motor is analyzed.The changes of harmonic components and vibration characteristics of electromagnetic force waves in two states are compared.Analysis of changes in parameters such as current,electromagnetic force and torque in the motor fault state and normal state can provide research directions for fault detection.Then,in order to improve the fault tolerance of the motor and reduce the hazard of the short circuit fault,it is necessary to detect the short circuit fault.Due to the obvious characteristics of the end short circuit fault,the detection difficulty is not high.However,the frequency of the turn-to-turn fault is high and the initial fault characteristics are not obvious.Therefore,it focuses on the detection scheme of the inter-turn short circuit fault;The research compares the detection effects of three detection schemes including detection coil,electromagnetic parameters and vibration characteristics on the inter-turn short-circuit fault.For the inter-turn short-circuit fault when the short-circuit position of the adjacent wire which is the most difficult to detect is close,analyze the detection accuracy of the three detection schemes,and finally discuss the advantages and disadvantages of the three detection schemes.Finally,in view of the ability of modular motor to withstand short-circuit faults,the influencing factors of motor short-circuit fault current and torque performance are analyzed from two angles of stator parameters,including slots,fault-tolerant tooth width and winding structure,and rotor structure parameters,including polar arc angle,pole arc eccentricity,magnetic rib width and V-shaped magnetic pole angle,etc.Choose a fault-tolerant solution that minimizes short-circuit current at the expense of minimum motor output;A variety of fault-tolerant strategies are proposed for single-phase end short-circuit faults and turn-to-turn short-circuit faults.Analyze and compare the variation of motor torque performance,electromagnetic force wave and vibration characteristics under different fault-tolerant strategies,and select the most suitable fault-tolerant strategy.