Effect of gear ratio on the dc motor efficiency of a minifuel-cell vehicle cruising at constant speeds

Abstract

The traction motor is a key component in a fuel-cell vehicle as it converts electrical energy supplied by a fuel cell into mechanical shaft work for vehicle propulsion. Motor size, torque rating and current consumption are important factors in the selection of the optimum drive motor for best energy efficiency. In a practical power train assembly, the motor is coupled to the wheel via a gearing system. This study focuses on the performance with respect to traction motor efficiency relative to the gear ratio selection and variable drive cycles to minimize the power consumption of the vehicle. A test bench with a 1 kW fuel cell was developed and tests were performed at constant speeds between 15 km/h to 30 km/h with different gear ratios. Among the measured and evaluated parameters using Eagle Tree and Inertia data loggers are rpm, current, torque and power. The results show that the gear ratio selection produces a variation in required motor input power at similar drive speeds. It also shows the optimal setting of the gear ratio of more than 70% that suits the best efficiency point of the DC motor according to actual driving requirements.

Keywords

• traction motor
• efficiency
• gear ratio
• pem fuel-cell vehicle
• constant speed