Design And Research Of Permanent Magnet Brushless DC Motor For Deep-sea Propulsion

In recent years, with the development of power electronics and permanent magnet materials, the permanent magnet brushless DC motor has more and more extensive application for its advantages of high power density, high efficiency, fast response, simple structure, reliable operation, good control performance, and so on. It has also become the preferred choice of underwater propulsion motor. According to the different installation position of the motor and propeller, underwater propulsion motor can be divided into integration and separation type. Compared with the separation propulsion motor, the integrated propulsion motor attracts more and more people’s attention for its compact and simple structure and without reducer.In this paper, the structure characteristics and operation principle of the brushless propulsion motor are analyzed, and the mathematical model of the propulsion motor is deduced. The calculation method of the main dimensions of the motor, the characteristics and design method of the stator and rotor structure, the selection of electromagnetic load, and the design method of the permanent magnet are studied. The motor electromagnetic calculation program is written with the Matlab programming language according to the equivalent magnetic circuit method, which is used to replace the manual calculation. And the program has a good man-machine interface, easy for users to adjust the motor parameters, so that the electromagnetic computing time greatly reduced. Procedures used interpolation to deal with the table problem, through the iteration method to automatically adjust some parameters of the motor. The electromagnetic computation is more efficient and accurate. Based on the results of Matlab electromagnetic calculation, the magnetic circuit calculation model of brushless propulsion motor was established under the Ansoft RMxprt module to verify the results of Matlab electromagnetic calculation, and to prepare for the finite element analysis. The finite element model of the motor is built under the Ansoft Maxwell 2D module, and the static and transient working states of the motor are simulated, and the no-load and full-load characteristics of the motor are analyzed, the output torque, current, speed, flux and other performance curve of the motor are obtained. The electromagnetic calculation program of Matlab is modified according to the results of finite element calculation. Through the analysis of the design scheme, the design method is verified to be correct, and the deviation is within the acceptable range. According to the design scheme, the reasonable value range of the parameters of the motor is summarized.In the last chapter of the paper, torque ripple of the permanent magnet brushless DC motor was analyzed, and focused on the analysis of cogging torque, derived its analytical expressions and given several more practical methods of reducing it.