High efficiency inductive charging for electric mini-cars. System design and prototype development of a charging system.

Abstract

One way to reduce pollution from the vehicle fleet is to electrify it. Electric vehicles needs to be charged quite often and a conductive charger with a plug has several disadvantages compared to wireless charging. This thesis describes the simulation and development of an inductive charger to a small electric vehicle. The charger can transfer 700-950 W at an efficiency of 87 %, and 1100-1200 W at an efficiency of 84 %. Measurements shows that the most significant contribution to losses occur in the secondary coil. An efficiency of 90 % is possible if the design of the secondary coil is improved. To deal with the high leakage inductance of the coils, resonant capacitor banks are placed in series with each coil. The load current is regulated by changing the duty cycle of the inverter. Further work is however needed for implementation of automatic control. Tests has been performed where the two coils are misaligned and when the gap has been increased. Results shows that a misalignment of 100 mm will give a total efficiency of 80 % which is still good. As the system has shown good performance the technology should be viable for charging vehicles but could also be applied in other areas.