Design And Analysis Of High-speed Brushless DC Motors

With the rapid development of Chinese aerospace industry,the performance requirements of the aviation motor have required higher and higher in recent years.Because of the special field of aerospace motors,there are many strict limits on both size and weight when we design the motor.However the common induction motor can’t meet the design demand for its size and running performance.With the evolution of modern power electronics technology and rare earth permanent magnet materials,the permanent magnet brushless DC motor(PM-BLDCM)which have a huge advantage in simple structure,light weight,small volume,high power density function will become more and more widely.However the PM-BLDCM in the application of aerospace research data is less at the moment.So this dissertation will design a outer rotor fraction-slot concentrated winding PM-BLDCM.Throughout the design analysis and optimization simulation of the motor,the rationality of the designed is verified.Which provides a theoretical reference for the application of high-speed PM-BLDCM in aerospace.First of all,the outer rotor fractional-slot of concentrated winding PM-BLDCM and the common DC motor on the structure and the way of excitation system are different.So this dissertation analyzes the PM-BLDCM structure,operation principle and mechanical properties at first.By means of the magnetic circuit method,the PM-BLDCM has accomplished the preliminary designed.Furthermore the motor parameters are presented in a simple spreadsheets.Secondly,the finite element method is used to simulate the no-load and full load characteristics of the motor.The voltage,current and torque of the motor are analyzed.I emphatically analyze the influence of permanent magnet motor magnetic field in three important parameters: the leakage flux factor at no-load,the calculating polar arc factor and the Air-gap factor.On this basis the finite element make an amendment the three parameters.Finally,the mechanism about cogging torque and the method about reduce the torque of permanent magnet motor are analyzed and studied in detail.By selecting the reasonable fractional-slot concentrated winding and pole-arc coefficients,PM shifting,skewed slots methods,the torque of the permanent magnet motor tooth groove is huge reduced.The motor which designed is reasonable.