A 3-speed drive for small electric vehicles

The future acceptance of small, battery-driven electric vehicles for private use in urban areas or local traffic will strongly depend on their performance, flexibility and costs, compared with their fuel burning counterparts. Costs can be lowered and performance can be improved by optimizing the overall efficiency of the vehicle's electric drive. As an example, the mechanical multi-speed transmission can be reduced in complexity by putting part of the speed/torque control of the drive into the electronic section. The paper describes the design philosophy of a three-speed electronic drive, based on a programmable logic device, a PWM power stage and a patented "variable transformer". Additional benefits of the module are automatic recharging of the batteries during the braking mode, and an inherent anti-block system (ABS).