Research On The Basic Electromagnetic Theory And Optimization Design Of The Alternating Pole Hub Motor

With the rapid development of automobile industry,the problems of the energy crisis and environmental pollution have exacerbated.So,the electric vehicle has become an important direction for future development of the automotive field,and the motor drive system of electric vehicles is the core of electromechanical energy conversion.The research of motor drive system takes vital significance.Permanent magnet synchronous motor(PMSM)has been widely applied in the field of small and medium electric vehicles thanks to the advantages of high efficiency?high power density.With the continuous development of motor and its controller and the wide application of high-power power electronic devices,the in-wheel motor drive has become an important developing direction and hotspot which reflect the feature of electric vehicles driving.Aiming at permanent magnetic material consuming and poor weak magnetic capacity of outer rotor motor,the consequent structure is introduced and studied in electromagnetic properties of consequent pole in-wheel motor(CPM)in this paper.In this paper,the basic structure of CPM is briefly analyzed,and compared with the conventional permanent magnet(PM)in-wheel motor structure.Then a mathematical model of CPM is established.According to the slot and pole matching,the air-gap magnetic flux density and magnetic leakage characteristics of 9-slot 8-pole and 12-slot 10-pole are compared and analyzed,and verified by finite element simulation.Secondly,the special cogging torque problem caused by the mechanical structure of PM motor,which is optimized in this part.The reason and the harm of cogging torque are analyzed.Then the commonly used method of weakening cogging torque is introduced.According to the analytical expression of cogging torque,from the slot and pole matching,pole arc coefficient optimization,changing the slot width to reduce the cogging torque by finite element analysis method.Then,the formation principle of the salient polarity of the CPM is analyzed in this paper.Based on the inductance characteristics of PMSM,the calculation method of the d-q axis inductance of the CPM is deduced.From the perspective of the magnetic circuit,the influence of the motor on salient polarity is analyzed.Finally,the saliency of the motor is studied through the finite-element simulation,to improve the saliency of the motor,further improving the capacity of the outer rotor-type hub motor weakening magnetic acceleration.Finally,on the basis of theoretical analysis and simulation,experimental prototypes of 48-slot 40-pole and 36-slot 32-pole of CPM are fabricated and tested based on the motor performance test system.The test system was used to test the back EMF,cogging torque and inductance of the prototype.The actual test results were compared with the finite element simulation to verify the rationality of the electromagnetic performance analysis.