Efficiency improvement in DC and AC motor powered electric vehicles

Electric vehicles seem to be a solution against the greenhouse gasses emission problem. The major problem of these vehicles is low autonomy, due to the low energy density of the batteries, compared to gasoline. A way of dealing with this problem is to increase the vehicle's efficiency, by minimizing the power losses. In this paper, ways of minimizing the power losses for DC and AC motor powered vehicles via adjusting the gear ratio and the motor's magnetic flux are studied. To do so, the losses of all parts of the electromechanic system are calculated as a function of the gear ratio λ, and the motor's magnetic flux CΦ, with the vehicle's speed and resultant force as parameters. It can be proved that for each pair of parameters there is an optimum set (CΦ, λ) that minimizes the vehicle's losses. Finally, the theoretical analysis is verified by experimental results.