Design Of Permanent Magnet Synchronous Motor For Electric Vehicles And Research On The Control System

With the rapid increase of the number of cars in the world, the consumption of oiland other scarce resources are increased, and the pollution of automobile exhaustemissions on the environment is increasingly serious, so the developments of newenergy vehicles have become the focus of countries around the world. The permanentmagnet motors which have high efficiency and high power density have become ahot applications, the research of permanent magnet synchronous motor for electricvehicles can solve the resource and environmental issues. A30kW permanentmagnet synchronous motor and its drive system for electric vehicles are designed inthis paper, meanwhile the structure of the motor is optimized and the motor controlsystem is researched, in addition, the performance of the motor which is designed tomeet the requirements of electric vehicles.The basic dimensions of the motor are designed by the field-circuit coupledmethod, and the motor2-D and3-D electromagnetic field are calculated by the finiteelement method to get the air gap coefficient, the pole arc coefficient and the leakagecoefficient, thus, the accuracy of the magnetic circuit calculation is enhanced. Therotor structure are designed and optimizated, the interior permanent magnet structurecan ensure the mechanical reliability of the rotor when running at high speed,meanwhile, the rotor structure is optimized by magnetic bridge, lightening holes andeccentric arc so that the performance of the motor are improved. The water coolingstructure of the motor chassis is designed, and the inlet structure is optimized so thatthe distribution of water flow is more uniform.The properties of flux-weakening control for permanent magnet synchronousmotor are researched in this paper, and the mathematical model of the motor isestablished to research current vector running track in the voltage and current limitcircle. The d-axis and q-axis inductances are calculated where the magnetic cross-coupling effect is taken into consideration, respectively, the flux-weakening controlsystem with and without considering the impact of magnetic saturation are simulated to analysis the feasibility of the control system and the impact of consideringmagnetic saturation on the control system.As the motor rotor rotates at high speed, the rotor mechanical strength at themaximum speed is analyzed and calculated. The stator core loss which is the mainloss of permanent magnet motor are calculated by iron loss separation method. Theoperating characteristics of the motor at the highest speed and the rated speed are gotby the field-circuit coupling method. In order to reduce the difference between theperformance computed and the actual one, the co-simulation of the control systemand the finite element model is established and the motor dynamic performanceunder different load are obtained.