Study on a Wide Speed Range Integrated Electrical Transmission System

The v-belt linked pulley based continuously variable transmission (CVT) has been adopted extensively in internal combustion engine scooters (ICES) and zero emission scooters (ZES), in which CVT is used to increase the starting torque and also extend the speed operation range of the engines or motors. However, because of the inherent frictional mechanism, the efficiency of general CVT is relatively low (40%~70%), it is highly dependent on driving conditions. In this paper, instead of using the low efficiency mechanical transmission mechanism or the complex flux weakening control technique, a new winding changeover technique is proposed to increase the low speed starting torque and also extend the high speed operation range for small to midsized electric or hybrid electric drives without increasing the rated size of the power switches, or decreasing the system efficiency/reliability. By eliminating the large friction loss of the CVT and the extra copper loss accompanied with flux weakening operations, the driving performance of the ZES can be improved significantly with the proposed techniques. The additional cost required to implement the proposed approach is the inexpensive electromagnetic contactors. Consequently, the proposed approach is very suitable for most cost sensitive ZES drives. Experimental results have demonstrated that the proposed approach exhibits superior performance when compared with the conventional solutions