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The purpose of this study is to examine a proper power system for a miniature vehicle called as “Commuter-car” that is expected to be used for commutation or shopping in urban areas. Before starting experiments, an investigation of actual commutation driving was made. It was found that the driving distance was generally short and that start-stop frequency was high at commutation driving in urban areas. As a result of this driving investigation, it was educed to introduce an electric motor traction method into commuter-cars. First, a small generator was added to a conventional electric vehicle (EV) to convert it into a series hybrid vehicle. The running range of this vehicle was confirmed experimentally to be extended much more than the base EV in transient driving. Therefore, it was judged that series hybrid system is reasonable to be applied to commuter-cars.

Recently, studies and developments have been underway in many countries to introduce a new type of car (hereinafter referred to as “Commuter car”), characterized by ultra smallness, energy saving and low pollution, for short-range purposes, for example commutation, in urban areas (1).In our previous study, the characteristics of electric motors were noticed, and the series hybrid system was focused to power commuter cars.Therefore, a simulated commuter car based on a small electric vehicle (EV) was set on a chassis dynamometer to test the basic items (2) . From these results, a new simulated series hybrid type commuter car that uses a high-power AC motor and a high-efficiency power generator was set on the bench.By acceleration/deceleration bench tests, selection of the reduction gear ratio and optimization of power supply from the generator were investigated in order to achieve both the performance necessary and sufficient for the city driving and power management.