| Electric vehicles have always faced the problem of insufficient endurance,so the extended-range electric vehicles have attracted much attention because it can greatly improve the cruising range.The generator of the range extender is an important energy supply device in the extended-range electric vehicle,and its performance directly affects the endurance of the extended-range electric vehicle.As electric vehicles have higher requirements for endurance and efficiency,the generators for range extenders need to meet the requirements of compact structure,high power density and high efficiency,which poses challenges to the design of generators.Taking the generator suitable for small commercial vehicles as the research object,this paper designs an internal stator permanent magnet synchronous generator to achieve the requirements of compact structure and high power density.Firstly,according to the application conditions and design requirements of the generator,the main dimensions,magnetic circuit structure and mechanical structure of the internal stator generator are designed in detail,and the key components of the internal stator generator were verified.After design calculation,the outer rotor outer diameter and inner diameter are taken as 270 mm and 246.6 mm,respectively,and the outer and inner diameters of the inner stator are 245 mm and 166 mm,respectively.The electromagnetic structure adopts a design scheme of 32-pole,24-slot and in-line segmented permanent magnets attached to the inner wall of the rotor.Then,the finite element calculation model of generator magnetic field is established based on JMAG.The key performance parameters such as magnetic density distribution,torque,back electromotive force,cogging torque and efficiency are calculated,and demagnetization analysis is carried out for extreme cases.In addition,a finite element simulation model of the generator temperature field is established,so the internal temperature field distribution of the generator is calculated.The influence of the inlet temperature and flow rate of the cooling water on the maximum temperature of the inner stator generator is studied.The results show that too high cooling water inlet temperature will significantly increase the maximum temperature of the generator,while too low temperature will consume more extra power.Therefore,the flow rate of cooling water should be selected within the range of 8-10 L/min.In order to verify the design of the internal stator generator and the finite element simulation results of the electromagnetic field and temperature field,the prototype was fabricated to carry out the temperature rise test experiment and the external characteristics and efficiency test of the generator.The results show that the highest temperature of the generator at the winding is 143.1℃,which is 8.84℃ different from the simulation results.The deviation between the experimental value and the calculated value is 6.18%,which verifies the reliability of the temperature field simulation model.At the rotational speed of 3000 r/min,the experimental values of the torque,current,power,power factor and efficiency of the internal stator generator are quite close to the finite element simulation calculations,and the maximum error does not exceed 1.5%.At the rated power,the generator efficiency reaches 96.2%,indicating that the design and finite element model of the internal stator generator are reasonable and reliable. |
