Optimization Design And Analysis Of Brushless DC Motor Rotor Structure For Compressor

Compressor is the core component of air conditioning system,The performance of an air conditioning system is largely determined by its performance.Electric motors convert electrical energy into mechanical energy,provide power for compressor,is the core component of the compressor,its performance has a great influence on the compressor.Brushless DC motor(BLDCM)is a kind of permanent magnet synchronous motor,Because of its remarkable advantages in controllability,reliability,economy and efficiency,widely used in compressor industry.For BLDCM,reducing large torque ripple during operation has always been an important topic in this research field.In the case of brushless DC motors,The torque ripple is generally divided into four categories,cogging torque fluctuations,PWM modulation ripple,commutation torque fluctuation,fluctuation caused by back EMF distortion.The cogging torque is caused by the slotting of the motor,is the inherent property of the motor,however the cogging torque of brushless DC motor is generally large,it will cause speed torque fluctuation,motor vibration and noise,especially in the case of variable speed drive,may bring resonance and greater noise,therefor,Reducing torque fluctuation caused by cogging torque is one of the main goals of brushless DC motor design.Scholars at home and abroad have done a lot of research on torque fluctuation caused by cogging torque,however,many optimization methods reduce cogging torque,reducing torque fluctuation,it has a negative impact on the average torque and efficiency of the motor,therefore,torque fluctuation is reduced by reducing cogging torque,And improving the efficiency of the motor is of great significance to the design of the motor.In this article,take a permanent magnet brushless DC motor for 700W compressor as an example,According to electrical mechanics and electromagnetic field theory,The basic assumptions and definite solution conditions are given,a two-dimensional field-circuit coupled time-stepping finite element calculation model for brushless DC motor is established.The cogging torque,torque fluctuation,loss and efficiency under no-load and load conditions are calculated and analyzed respectively,the basic performance parameters of the motor and optimization direction are obtained.For the designed motor,an optimization scheme based on the rotor structure design is proposed,to reduce cogging torque,reducing torque fluctuation,Improve motor efficiency.The optimized motor model is established by finite element method,calculation and analysis of cogging torque,torque fluctuation,loss and efficiency under no-load and load conditions of the motor,a useful conclusion is drawn through calculation,the feasibility of the optimization method is verified,it has certain guiding significance for the design of the motor.