Patent GB-319834-A (GB)
Title: Improvements in electric power supply apparatus
IPC: H02J3/38
Filed: 1928-07-03
Abstract: 319,834. General Electric Co., Ltd., and Wilson, W. July 3, 1928. Supplying consuming devices; starting prime movers.-In a system for automatically starting a generating plant in accordance with power demand in which the prime mover is started by the generator and a battery, a change from starting to running connections is controlled by a reverse current relay connected between machine and battery. Completion of the starting connections is controlled jointly by this relay and by a starting relay responsive to power demand, and the starting relay may shut down the plant upon a fall in power demand. A compound wound generator 1 has a starting field winding 6 and compound winding 4, the respective circuits being controlled by a starting contactor 7 and a running contactor 9. The battery 11 is of relatively small capacity and the load circuit passes through the fine wire winding 25 of a starting relay and winding 29 of an auxiliary relay and the contacts 41 of a latched-in protective switch. A predetermined load closes the contacts 28 of the starting relay, completing a circuit including the coil 25, throttle-control coil 48 and polarizing coil 18 of the reverse current relay. This relay, which is biassed by a spring 21 to close its contacts 23, carries the circuits through coil 8 of the starting contactor and the plant starts up. The armature circuit includes the coil 35 of the protective switch and the coil 14 of the reverse current relay. The former has a time delay, and failure of the plant to take load within the time limit causes the latch 38 to be lifted and the spring 43 to open the starting circuit at contact 39 and the load circuit at contact 41, thus protecting the battery against prolonged discharge. When current reverses in the coil 14 the reverse current relay opens contact 23 and closes contact 22, de-energizing the starting contactor and protective switch coil 35, and closing the running contactor 9. Rise of load above the rating of the starting relay coil 25 causes the coil 29 of the auxiliary relay, which may be shunted by a resistance, to close contacts 31, 32 in parallel with the starting relay contacts and to short circuit the coil 25 at contacts 31, 33. Fall of load restores the starting relay to its active condition until the limit is reached at which it opens its contacts 28, and the plant is stopped and control apparatus restored to its idle condition. The auxiliary relay may be dispensed with if the starting relay has a thick wire coil in series with the fine wire coil, the latter being adapted to be short-circuited by auxiliary contacts on the running contactor. Should the engine stop during load demand the control apparatus attempts to re-start it, but the protector switch then operates. The protector switch may be released by a thermal element. The engine may be stopped by lifting the exhaust valve, retarding the ignition, &c. and in one form in which the engine is started on petrol but runs on oil movement of the starting relay to the open position whilst the auxiliary relay is open de-energizes a solenoid to cause the fuel reservoir to be drained. Filling of the reservoir with petrol for starting and the change to oil may be controlled by auxiliary contacts on the starting contactor.