Design And Research Of Brushless DC Motor In Electric Automobile

With the society development, the demand of energy is increasing quicklyand at the same time people are more concerned about environment. Hence,electric cars become more and more significant and under the spotlight. Thewidespread adoption of electric cars could improve air quality remarkablybecause no pollution produced, also it could alleviate the pressure of energyshortage. Therefore, the research on electric cars has higher research value.The basic structure and working principles of brushless DC motor areintroduced in this thesis. Several common designs of the motor electromagneticare introduced as well. With the electromotive force star map, the slot-polecombinations of fractional slot and concentrated winding are further analyzed.Slots and poles of the brushless DC motor which are designed in this thesis areselected according to the research. Later, the design of the drive motor ontologywas finished by using the method of combining the magnetic circuit calculationand finite element calculation, which also makes sure the odd and even slotpermanent magnet motor scheme. The analysis of the odd and even number slotpermanent magnet motor in back electromotive force, load current,electromagnetic torque and the cogging torque was performed by the finiteelement software Ansoft. Due to the significance of cogging torque in thepermanent magnet motor performance and quality, the causes, the effects and themethods of how to weaken the cogging torque were analyzed in this thesis. Theperformances of the odd and even number slot motor were compared based onthese research and the results showed that the performance of the even numberslot motor is better than the odd number slot one and the magnetic fielddistribution is more homogeneous. So my thesis is focused on the main reason ofthe unbalanced radial magnetic force and the effects when motor runs. In conclusion, even number slot motor was selected in this thesis becausethe odd number of Z will induce the unbalanced magnetic pull which isunfavorable to the overall performance of the motor. At last, based on the results,a program of the design of permanent magnet motor was written with VBlanguage which makes the computation more intelligent and finalises thecomputer aided motor design.