Design And Comparative Analysis Of Surface And Interior Fault-Tolerant Permanent-magnet Vernier Machine

With the increasingly prominent energy issues and the rapid development of high and new technologies such as wind power, electric vehicles, wave power and so on, how to further enhance the reliability of the electrical system and the power density of machine in direct-drive fields has become a hot area of research. Traditional fault-tolerant permanent-magnet machine has the merits of simple structure and high reliability, but the power density of machine at low speed is not high enough for the requests of direct-drive applications. The torque performance at low speed can be improved in magnetic-geared permanent-magnetic motor, but it has multilayer air gap, resulting in complicated structure and difficult manufacture. In recent years, permanent-magnet vernier(PMV) machine with simple structure and high torque density is widely considered to have broad prospects in direct drive system. This machine is based on the “magnetic gear effect”, which makes full use of other harmonic components of magnetic field besides the fundamental harmonic by introducing the modulation teeth on stator, so that the high torque output can be achieved at low speed condition with a small volume, on this basis, combining with fault tolerant motor structure makes it have high reliability as well.In this paper, five-phase fault-tolerant PMV machines are researched, some reasonable design and optimization are made to get the advantages of high reliability and high torque density, finite element method is used to compare and analyze the performances of machine. The main study results are included as follows:1. Based on the “magnetic gear effect”, the analytical expression of modulation principle in PMV machine is given, and the modulation process is described and verified by the finite element analysis results.2. Three different fault-tolerant surface PMV machines with bipolar, unipolar, and hybrid magnetic materials surface mounted permanent-magnet structure respectively are designed and proposed. The design and optimization process is described, and the finite element method is used to analyze the static characteristics of above machines, including magnetic field, back EMF, air gap flux density, torque performance and fault tolerance.3. A fault-tolerant interior PMV machine with spoke type interior permanent-magnet structure is designed and proposed, the design and optimize process is described in this paper, and the finite element method analysis is used to analyze the magnetic field, back EMF, torque performance, demagnetization, loss and other characteristics. Performance of the interior PMV machine is also compared with that of the bipolar surface PMV machine and a conventional interior permanent magnet machine. Besides, a joint simulation of Maxwell and Simplorer software is made on the proposed interior PMV machine.4. The prototype machine is designed and manufactured, the corresponding hardware and software platforms are also built, and the theoretical analysis is verified by the experimental test results.