Power Transformer Design For Tethered Underwater Vehicles

Abstract

Tethered underwater vehicles benefit from the smallest possible tether through reduction of both tether handling gear and tether drag. If the vehicle is powered through the tether, a transmis- sion voltage in the range of one to three kilovolts usually results in the smallest tether. AC power transmission system can use trans- formers for conversion of the high voltage to service levels. Transformers for underwater vehicles are designed with different goals than conventional transformers. Weight is a prime consider- ation for any neutrally buoyant vehicle and thus most other con- straints, including efficiency, are relaxed in pursuit of lower weight. Design starts with a prioritized list of constraints. Non-linear optimi- zation can then apply these constraints to the basic electro-magnetic and thermal equations governing a transformer. The result is a tenta- tive core and winding design that can be compared with the original goals and iterated to achieve any necessary compronlises. An example design for a 400 Hz, three-phase, oil cooled, pressure compensated, toroidal system delivering 20 kilowatts DC to a vehicle is detailed. The design target and "as manufactured"' parameters are compared. I INTRODUCTION