Efficiency analysis of powertrain with toroidal continuously variable transmission for Electric Vehicles

In order to extend electric mileage per charge of Electric Vehicles (EVs), the powertrain efficiency should be further improved. A possible solution is employing transmission which is properly optimized for EV. Continuously variable transmission (CVT) is especially suitable, because it maintains the operating condition of electric motor being closer to the most efficient region even while vehicle speed is changing. In this paper, a toroidal CVT and a single ratio transmission are compared by numerical simulations regarding the overall efficiency. Toroidal CVT has an advantage for high torque-low speed region and low torque-high speed region. However, regarding the rest, the efficiency degrades in contrast. In order to improve the overall efficiency, the best implementation approach is introduced.