Research And Design On A Permanent Magnet Electrical Machine Combined With A Magnetic Gear

A novel magnetic field modulation gearing transmits torque by magnetic force with high density and efficiency, and could be a potential substitute of a mechanical gearing if used in lustration, low temperature, high altitude environment etc. The development of high performance rare-earth permanent magnet material and its successful application in electrical machine, make it possible to provide more torque density and efficiency for a modern permanent magnet machine compared with for an induction motor.A permanent magnet electrical machine combined with a field modulation magnetic gear has been presented in this paper. The paper describes the fundamental structure of an outer rotor brushless PM motor is embedded into a novel magnetic gear. Merits of the permanent magnet electrical machine and the novel magnetic gear are combined together for realizing a high toque low speed drive. The research results application prospect is widespread, may be applied in the military domain (ship direct drive), the transportation (electric locomotive, electric automobile direct drive), the renewable energy development (wind power generation), the advanced manufacturing industry (machine tool direct drive) and so on.As one part of the national 863 program research project"Research on an efficient large torque direct-drive permanent magnet combined electrical machine system"(2007 AA05Z233),The text concentrates on the design of a permanent magnet electrical machine combined with a magnetic gear.This article around a permanent magnet electrical machine combined with a magnetic gear expands research, do the following tasks:1) Base upon the analytical approach of electromagnetic field as a starting point, in cylindrical coordinates find the analytical solution of Laplace's equation in a certain annular region of the air gap. Combine the finite element method, solve overall field vector potentials in an electrical machine, and lay the foundation to calculate other physical quantities.2) Analyze deficiencies of mechanical gears and traditional magnetic gears, research magnetic field modulation magnetic gearing which is the key part of the combined electrical machine work. For the characteristic of the device with two layers of air gap, whose input rotor and output rotor turn reversely, extend numerical and analytical combined method of magnetic field calculation, and establish the corresponding program. Both in inner layer air gap and in outer layer air gap the magnetic field has many kinds of harmonic component existence, but the electromagnetic torque is nearly the sole fundamental wave ingredient, the calculation result by way of numerical and analytical combined method is consistent with the theoretical analysis.3) After using the inner rotor's space of the field modulation magnetic gear, considering processing, assembly and so on feasibility, has completed the electrical machinery topology innovation, i.e., designed the permanent magnet electrical machine combined with the novel magnetic gear. With the aid of the numerical and analytical combined method, has realized the magnetic field calculation under the condition that the inner rotor and the outer rotor rotate with free pace and different direction. Parameters of the induced electromotive force and the electromagnetic torque and so on of the novel motor have been calculated, and it is not difficult to catch the maximum value of cogging torque. Has designed a low speed big torque highly effective electrical machine combined with a novel magnetic gear according to certain target requests, and developed the prototype.4) The experiment has proven the union of a novel magnetic gear and a permanent magnet electrical machine in the structure innovation successfully. The electrical machine combined with a novel magnetic gear runs at a high torque density with a stable movement effect. The high torque density, the high transmission efficiency and stable movement result of the magnetic gearing prototype are also obtained. The induced electromotive force and electromagnetic force of the combined electrical machine have obtained consistently with the analysis by the way of numerical and analytical combined method, which proves the proposed method is correct and effective in the multiple airgaps situation.The novel electrical machine combined with a magnetic gear has a compact structure, high torque density, high power factor and the protection ability when overloaded, suits in the low speed high torque direct drive system. The smooth movement of the novel electrical machine combined with a magnetic gear has been obtained, which proves the success of the structure and the design algorithm innovation, has increased the new way for the low speed high torque electrical machine design.