Efficiency analysis of electric vehicles, with emphasis on efficiency optimized excitation

An attempt is made to quantify the efficiency improvements in electric vehicles which can be obtained with optimized flux control. A constant current ratio control strategy and a true optimum flux control strategy are evaluated and compared in stationary speed-torque working points and for standard driving cycles. This is done by the use of a computer-assisting analysis program for electric vehicles. Two different systems are analyzed; a smaller vehicle with a DC motor drive, and a larger vehicle with an induction motor drive. The constant current ratio control strategy is shown to be a simple alternative to true optimum control for DC motors. Driving cycle calculations show efficiency improvements of up to 5-6% with optimized flux control.<>