Applications of SR Drive Systems on Electric Vehicles

Abstract

As the continuous growth of global vehicle production and owned, the problems brought by vehicles are conspicuousness day after day. These problems are much more serious in China. Thus developing zero emission electric vehicles have become the main scientific research projects in many countries around the world in 21st century. Energy-saving motor drive technology has become one of the key points to the EV commercialization. In the present electric vehicles, there are several main drive systems include the chopping system of DC motor, the variable frequency drive system of induction motor(IM), the drive system of permanent-magnet motor(PM) and switched reluctance drive system(SRM), etc. The DC machine has been faded gradually in the electric vehicle drive system for the reason of high startup current, huge volume, low efficiency and poor reliability. Even worse, the carbon body and the commutator which are not suited for high speed movement need to be changed frequently. The variable frequency drive system of IM has a small torque fluctuation, but with low efficiency especially in the low speed stage. When the electric vehicle is grade climbing, the torque output is small and the current is high. Although the permanent-magnet motor is of high efficiency, the manufacturing technique is very complicated and the machine will lose effectiveness because of the demagnetization in high temperature. So it is not the perfect way. The structure of the SR Motor is firmly and stable. The SRD system has a high reliability, wide range of speed regulation, high efficiency, low startup current and large torque output, all of which are especially suited for the work condition of the electric vehicles. The application of SRD on electric vehicles is affected by the torque fluctuation and strong noise. In a word, performance comparisons of the three motors are indicated in the following table 1. Because of its own characteristics,electric vehicles motor drive system should meet the following demands: 1. Output a large torque under base speed to meet the requirement of starting, accelerating, climbing and some other complicated working conditions. 2. Output constant power above the base speed in order to adapt max speed, overtaking and so on. 3. Maximize motor efficiency over the whole speed range to extend endurance mileage. From the table, the SRM has more advantage than the other motors. Many control different strategies have been proposed for the torque fluctuation task . Full rotor pitched insulating non-magnetic colloid techniques of SRM and SRM fuzzy logic