Design Of Electromagnetism And Research On Cogging Torque Of Brushless DC Motor

In recent years, the Brushless Direct Current Motor(BLDCM) used in high-performance speed and position control system more and more widely with its small size, high efficiency, easy maintenance, good speed performance without excitation losses and other advantages. However, due to the interaction between the permanent magnets and the armature, the cogging torque emerged and produced vibration and noise, affecting the accuracy of the control system. Therfore, both the design of BLDCM and the study of cogging torque are of great significance.This paper firstly introduces the development of BLDCM, summarizes the research status of BLDCM, and focuses on the development status of BLDCM body design and cogging torque.Secondly, on the basis of the basic structure and working principle of BLDCM, several important basic physical formulas, which are existed in the electromagnetic design of BLDCM, are derived in detail; the cause of the cogging torque of BLDCM and the corresponding weakening methods are analysed in-depth.Thirdly, on the basis of the electromagnetic design theory of BLDCM, a continuous operation BLDCM, which rated power is 30 W, rated voltage is 24 V, rated speed is 1350 rpm, is designed by hand calculation method. The rationality of the design result is verified with the RMxprt design software, and the finite element analysis results of the BLDCM are presented yet.Finally, according to the characteristics of too large amplitude of the designd BLDCM, the weaken method of its amplitude has been studied from two perspectives, that changing a single parameter and the optimal combination of parameters.In the study of changing a single parameter to weaken cogging torque, the slot width, the auxiliary tank of stator and unequal thick pole influence the cogging torque has been analysed respectively. The influences of other properties of BLDCM, such as no-load flux density, no-land back-EMF, the torque and current of load, have been studied because of the changes of these parameters. The results show that the change of single parameter in these three parameters can weaken the amplitude of cogging torque with varying degrees and has a certain influence of other properties of BLDCM.In the study of the optimal combination of parameters to weaken cogging torque, based on the parameter optimization theory, the corresponding optimization model is established by writing the genetic algorithm program, and the optimal parameter values emerged by calculation, and compare these values with the results of genetic algorithm optimization of Maxwell 2D. On the basis of the above, the influence of the cogging torque and other properties of BLDCM have been analysed by using the finite element method on the change of the combination of parameters. The results show that the combination of parameters can be better weaken the amplitude size of the cogging torque in the premise of without seriously affecting other properties of the motor.