| The trend of transition from fuel vehicles to electric vehicles(EV)is inevitable.With low cost,reliable performance and mature control technology,asynchronous motors have an important share in drive motors of EV.Unlike industrial motors running at rated point,drive motors of EV run in a range,while the iron loss in asynchronous motor accounts for more than 50% of total losses at load ratio of 10%.Modern drive system in EV is based on FOC(Field oriented control,FOC)technology.Considering that FOC is loaded on the motor in the form of SVPWM,it is important to study the influence of different modulation parameters on the iron loss of asynchronous motors under different load conditions.The research is significant in improving efficiency of the asynchronous motors.In this paper,the dynamic mathematical model equation of asynchronous motor is deduced.Considering its high coupling degree,multivariable and nonlinear characteristics,and coordinate transformation of equation is carried out for using FOC easily.Based on the RTW,the simulation of discrete FOC control model is built.The RTW transformation of the SVPWM module is carried out to control the motor through DSP,which reduces the difficulty of control code development significantly.The paper introduces the mechanism and calculation method of core loss,and briefly describes the measurement methods of other losses.A finite element model of the asynchronous motor is built,and the different excitations in Simulink are applying on the asynchronous motor model.Under different torques,different amplitude modulation ratios and different modulation frequencies,the iron loss of the motor is researched.The influence of different modulation conditions on the distortion of the magnetic density and the influence on the degree of rotational magnetization in the typical position in stator motor are quantitatively analyzed.Finally,a motor test platform was built,and the code generated by the model is loaded onto the motor through the TI kit.According to the measurement results,the iron loss of the motor increases with the increasing modulation frequency,and decreases with the increasing switching frequency.The influence of the change of amplitude modulation ratio and the torque on the iron loss is related to whether it is in the low torque region. |
