Design Of High-Efficiency Permanent-Magnet Motors Combined With Electric Vehicle Driving Cycles

In recent years,the efficiency improvement of permanent magnet(PM)motors for electric vehicles has become a research hotspot in the field of PM motors.Traditional methods of improving the efficiency of PM motors are mainly realized by increasing torque densities and reducing loss.However,these methods only focus on the maximum motor efficiency,but ignore specific driving cycles of the motor.Once there is a big difference between the high efficiency region and the motor operating area,the motor will operate in the low efficiency mode in essence.In this paper,a design method of high efficiency PM motors combined with driving cycles is presented.Based on the depth analysis of the efficiency Map of PM motors,the movement principle of the high efficiency region is obtained and the corresponding regulation methods and design process are given,which lay the groundwork for the design of high efficiency PM motors combined with driving cycles.By employing the regulation principle and methods to design PM motors,the expected results can be achieved with only a small amount of simulation.Thus,the design result can be predicited and the simulation time can be greatly saved.Different from traditional methods to improve efficiency,the proposed method can optimize the motor efficiency Map globally according to the motor operating concentrated area,resulting in the expansion or movement of the high efficiency region in the efficiency Map.The focus is on the improvement of the matching degree between the motor operating concentrated area and the high efficiency region to maximize the efficiency under corresponding running states and save energy.The main research results of this paper are as follows:1.The production mechanism,expressions and influencing factors of loss in the efficiency composition are studied.Besides,by introducing the theory of voltage and current limiting equations,the forming mechanism of efficiency Map of PM motors is studied ulteriorly.2.The EV driving cycles are introduced.The motor operating area is obtained by cycle curves and kinetic equations of EVs,and is associated with the efficiency Map.The significance of high efficiency PM motor design combined with driving cycles isexpounded.3.Based on the efficiency and loss formulas and the forming principle of efficiency Map,the interregional connection equations are established in the constant torque area of PM motors,and then the conditions to be satisfied for the high efficiency region are deduced.Then,the regulation principle of the high efficiency region is revealed and verified by finite element analysis(FEA).The thermal analysis is carried out on the PM motor before and after the regulation of the high efficiency region to verify the practicability of the regulation principle.4.Three methods of regulating the high efficiency region are proposed,and the generality of regulation principle is verified by using PM motors with different phase numbers,winding forms,PM structures,and inner or outer rotors.The regulation methods are theoretically analyzed and the FEA is employed to verify the results.Also,the corresponding design flows of high efficiency PM motors are given.5.A prototype is manufactured,and the motor experimental platform is built based on the d SPACE real-time simulation system.The efficiency of the motor is measured,and the correctness of the theoretical analysis and the finite element simulation results are verified.