A highly efficient contactless electrical energy transmission system

This paper proposes a new concept for contactless electrical energy transmission system for an elevator and an automated guided vehicle. The system has rechargeable batteries on the car and electrical energy is supplied at a specific place. When electric power is supplied to the car, it runs automatically and approaches the battery charger. Therefore, a comparatively large gap is needed between the primary transformer at the battery charger and the secondary transformer on the car in order to prevent damage which would be caused by a collision. In this case, a drop of the transformer coupling rate due to the large gap must be prevented. In conventional contactless electrical energy transmission technology, since electric power is received by a pickup coil from a power line, a large-sized transformer is required. When the distance over which the car runs is long, the copper loss of the line also increases. The developed system adopts a high-frequency inverter using a soft switching method to miniaturize the transformer. The system has a coupling rate of 0.88 for a transformer gap length of 10 mm and can operate at 91 % efficiency. (C) 2004 Wiley Periodicals, Inc.