Hiroshi Katada

The Efficiency Improvement of Electric Vehicles by Regenerative Braking

Generally in electric vehicles regenerative braking is incorporated to increase urban driving range on a single charge and to get the same brake torque as engine brake. An analysis of the regenerative operation by thyristor chopper control is described. Firstly, to clarify regenerative efficiency, the calculation of various losses such as commutation loss and thyristor loss which arises at the braking mode is discussed. The regenerative efficiency calculated from the above losses agrees closely with test results. Secondly, a newly developed automatic field control (AFC) regenerative braking system is introduced. This AFC regenerative control system uses a shunt motor, the field current is controlled inversely proportional to motor speed and regenerative operation is obtainable by low motor speed. This system is suitable for electric vehicles. Thirdly, it is noted that utilizing this AFC regenerative brake control, actual urban driving range can be increased by approximately 16%.