Design Of Fractional-slot Concentrated Winding PM Machines For Low-speed Traction Applications

Over the past decade,due to the sharp increase in the use of fossil fuels,the energy crisis is becoming more and more serious.Meanwhile,the air pollution caused by the burning of fossil fuels has become a growing concern.Traction motor instead of the traditional internal combustion engine as the core of transportation is a green sustainable development strategy.The low-speed electric vehicles is one of the typical cases,it has been widely applied in medium and small cities,campus.Permanent magnet motor(PMSM)has become the development trend of low speed traction motor because of its high efficiency,high torque density and high power factor.At the same time,fractional slot concentrated winding is widely used in permanent magnet traction motor because of its advantages such as small copper loss,short winding end and simple processing.It is a hot research topic to study the high performance fractional slot concentrated winding low speed permanent magnet traction motor.In this thesis,the theory of fractional slot concentrated winding is analyzed firstly,and then the difference between fractional slot concentrated winding and integral slot winding is compared.At the same time,the constraint conditions of the slot winding of the fractional slot concentrated winding are determined.Then a fractional slot concentrated winding permanent magnet motor is designed in combination with low speed traction motor project.The specific meaning and selection method of the main parameters of the motor during the design process are analyzed.At the same time,the electromagnetic load,pole slot combination,rotor structure and material selection were analyzed and selected.In the process of optimizing the design of the motor,the split ratio,the permanent magnet and the cogging torque are optimized,and the torque ripple suppression of the motor is analyzed and studied.Later the electromagnetic performance of the motor is simulated and analyzed.At the same time,the loss of the motor is analyzed and calculated,the calculation method of the main loss of the motor is determined,and the calculation method of the motor's d and q axis inductance is studied.Then,the reliability of the motor is analyzed,and the reliability of the motor is determined by the permanent magnet demagnetization,the mechanical stress calculation and the temperature rise calculation.Finally,a low-speed permanent magnet traction motor prototype is designed.Through a series of experiments,it is confirmed that the prototype performance has basically reached the design requirements,so that the theory and practice are closely linked,and the motor optimization design has been further understood.In summary,the fractional slot concentrated winding permanent magnet motor is very suitable for low-speed traction field,this paper discusses the design method in detail,which provides a reference for the design of this kind of motor.