Research On The Reliability Of Stator Permanent Magnet Machine System

In the field of electric vehicle,aerospace,rail transportation,offshore wind generation,etc.,safety and continuous operation capability of electric machines are two major concerns,which are directly related to the reliability of machine systems.Therefore,it is of great practical significance to study the relationship between the structure and reliability of permanent magnet(PM)machines.Stator permanent magnet(Stator-PM)machine is a new type of brushless permanent magnet machine developed on the basis of rotor permanent magnet(Rotor-PM)machine.It not only has the characteristics of high power density and high efficiency of PM machine,but also has strong anti-demagnetization ability and easy heat dissipation of PM,simple and firm structure of rotor,so it has great application prospects.Flux-switching PM(FSPM)machine is the most prominent representative of Stator-PM machine.Therefore,this dissertation takes FSPM machine system as the research object to analyze its reliability.Firstly,the failure modes and effects of machines are studied.Secondly,the influence of machine structure,winding phase number,winding distribution and fault tolerance success probability on the winding reliability is studied.Thirdly,the shaft voltage of machine is studied.Finally,the accuracy of the reliability assessment and the shaft voltage analysis are verified by the three-phase FSPM machine system fault experiment and the inherent shaft voltage measurement experiment.The results of the reliability assessment and the shaft voltage provide recommendations for high reliability machine design.The research results of this work are as follows:1.The functional model of machine is established by analyzing the function of components of similar product.The failure modes and causes of Stator-PM machine are analyzed from the angle of affecting the function of components.The failure factors and mechanism of main components of Stator-PM machine are discussed.2.The reliability evaluation model of three-phase FSPM machine system is established,and the reliability evaluation is carried out.The importance of each part in the assessment model is evaluated.Based on the reliability analysis method of Markov model,a fast Markov reliability calculation method is proposed.The reliability of the system with different number of faults is compared and discussed with this method.The influence of the maximum number of faults on the reliability evaluation results is discussed.3.The relationship between the phase number and the reliability is studied.The calculation equation between the mean time to failure(MTTF)of winding and the phase number is proposed.Analyze and calculate the reliability of distributed winding structure and concentrated winding and compare their reliability.The effect of multi three-phase winding structure and fault-tolerant success probability on reliability is analyzed.4.The reliability of four-phase,five-phase,six-phase and nine-phase FSPM machine systems is evaluated under the same evaluation conditions.The reliability of different phase number FSPM machine system with fault-tolerant tooth structure and hybrid excitation is evaluated.The influence of machine structure on reliability is discussed.5.The mechanism of the inherent shaft voltage and control shaft voltage are analyzed.The shaft voltage simulation model is established to study the effects of machine speed,shaft material and size,PM material,rotor eccentricity and armature current on the inherent shaft voltage.The distribution of coupling capacitance of three-phase FSPM machine is analyzed,and the influence of their values on the control shaft voltage are discussed.6.The experimental platform of three-phase FSPM machine is built,and the drive and control circuit based on DSP is constructed.By measuring the winding current and output torque of three-phase FSPM machine in the case of open circuit fault and current sensor fault,the simulation results in reliability evaluation are verified to ensure the accuracy of evaluation.The inherent shaft voltage of three-phase FSPM machine is measured at different speeds.The experimental results are compared with the simulation results to verify the accuracy of the inherent shaft voltage research.