GB428603A - Improvements in or relating to emergency electric supply systems - Google Patents

Abstract

428,603. Supply systems; charging and discharging batteries; equalizing load on generators. OLDHAM & SON, Ltd., 36, Hyde Road, Denton, near Manchester, and WALKER, C. B., 38, South Bar, Banbury, Oxfordshire. June 11, 1934, No. 16655/33. [Class 38 (iv)] Substituting sources in service.-In an emergency supply system, on failure of the main supply a stand by battery is connected to the load but on restoration of the main supply the battery continues to supply the load until it is discharged to a predetermined extent. The battery is charged from the main supply source either directly or through a motor generator or converter, or, in the case of D.C. supply, through a booster. A.C. mains 6 are normally connected through a step down transformer 2 to load circuits 5 through contacts 27 and 25 of a rotary switch 22. The mains are also connected through contacts 9, 11, 12 of a further rotary switch 7 to supply a motor 4 driving a D.C. generator 3 which is connected to charge the battery 1 through contacts 10, 17, 18 on the switch 7 and contacts 24, 26 of the switch 22 in series. The switches 7, 22 are operated by springs wound up during operation of the generator 3 and are held by electromagnetically operated catches 36, 37 and 49, 50 bearing on notched discs 40, 47. Coils 51, 52 controlling catches 49, 50 for the switch 7 are supplied from the battery and are controlled in accordance with the state of charge of the battery by a relay 56 controlled by a switch 56 and sensitive to the voltage of the battery and arranged to energize either the relay 51, or 52 according to whether the battery 1 is fully charged or slightly discharged. Coils 35 and 34 are also supplied from the battery and are controlled by a relay 33 sensitive to the output voltage of the transformer 2 which energizes either coil according to whether the main supply is available or not. The circuits of the coils are prepared and broken by a pilot switch 42, 52 or 53 and contacts 43, 45 or 54, 55 rotatable with their respective switches 22 or 7. The circuit of the coil 35 is also controlled by the pilot switch 53 so that it is only completed when the switch 7 is in the battery charging position. The arrangement is such that on failure of the mains supply relay 33 falls off and completes the circuit of the coil 34 through contacts 33<1>, and the switch 42 which is then bridging contacts 43. The switch 22 is rotated to the position in which the battery supplies the load through contacts 24, 28, the switch 42 preparing the circuit for the coil 35 through contacts 45. On restoration of the main supply, contacts 35<11> of the relay 33 are closed and coil 35 is energized through the switch 42 and contacts 45 only if and when the switch 7 is in the charging position shown in which the switch 53 bridges contacts 54 thus completing the circuit of the coil 35. Switch 22 is then rotated and reconnects the main supply to the load, also connecting the battery to the generator. When the battery is fully charged, coil 51 is energized by operation of the relay 56<1> and releases the catch 49 so that the switch 7 is rotated to disconnect the battery from the generator and the motor 4 from the main supply. At the same time a circuit for the coil 52 is prepared so that when the battery voltage has fallen to a predetermined extent relay 56<1> causes energization of the coil 52 and reconnects the battery to the generator and the motor to the mains. Should the mains supply be restored before the battery voltage has fallen the battery continues to supply the load until relay 56<1> operates to put the battery on charge, when the circuit for the coil 35 of the switch 22 will be completed to connect the mains to the load and complete the charging circuit. In a modification, in order to limit the load on the normal supply, a current vaporizing relay may be provided to connect the battery to the load or a part thereof when the demand exceeds a predetermined value.