GB413668A - Improvements in or relating to electric ship propulsion systems - Google Patents

Abstract

413,668. Systems for transmitting mechanical power; synchronizing. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, and GARRARD, C. C., c/o General Electric Co., Witton, Birmingham. Nov. 14, 1932, No. 32160. [Class 38 (iv).] Running generators in parallel.-In a ship propulsion system a propulsion motor is supplied from a number of alternating current generators A, B, C operating in parallel, each generator being driven from a separate prime mover, such as a Diesel engine, provided with speed controlling means, and choke coils D, E, F being provided interconnecting the generator winding to facilitate self-synchronization of the alternators and to limit the synchronizing currents. A centre tapped choke coil D1-D3, E1-E3, F1-F3 is provided for each phase of each generator, the centre tapping points of all the coils being connected together to form a neutral point. The extremity of each generator phase winding is connected to one end of its corresponding choke coil and to the opposite end of the choke coil of the corresponding choke coil in the adjacent generator. Thus, phase winding A1 is connected to the top end of coil D1 and the bottom end of coil E1 and so on. The coils thus arranged offer low impedance to load currents but limit synchronizing currents. The coils may be connected between the alternators and the bus-bars and, if the alternators are delta connected, they may be arranged between only two out of the three sets of terminals between the alternators and the bus-bars. If only two alternators are used only one set of choking coils is sufficient. The coils are provided with switches 7, 8, 9 which short circuit them when the corresponding alternators are not operative. Synchronizing of the alternators and starting of the motor is effected with the alternators running overexcited at low speed. Speed control is effected by varying the number of alternators in service and by adjusting the speed of the prime movers. Two separate groups are provided for port and starboard propellers or for inner and outer propellers in a quadruple screw ship. The motors may be asynchronous or synchronous. Separate or common control may be provided and control handles may be arranged to control engine starting, alternator synchronization, motor starting and motor synchronization suitable interlocks being provided to prevent further movement of the handles before synchronization is completed. Interlocks are also provided for preventing connection of an alternator to the bus-bars unless its control handle is in the " off " or engine starting position. Manoeuvring is effected with the alternators delivering low voltage at low speed.