GB436952A - Improvements in and relating to electric converter systems - Google Patents

Abstract

436,952. Converting. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London. April 16, 1934, No. 11434. Convention date, April 14, 1933. [Class 38 (ii)] To avoid momentary interruption of connection in a system comprising A.C. and D.C. lines 1, 2 interconnected through a discharge device 8 having a reversing switch 12, 22 to allow of operation as a rectifier or as an inverter an auxiliary converter of any type is provided which is reversely connected with respect to the main converter and ensures the transmission of energy at the moment when the change in the connections of the main converter takes place. In the form shown, the auxiliary converter is a gridcontrolled discharge device 103 controlled by switches 112 and 122 to enable it to operate either as a rectifier or as an inverter. The operating coils 20, 120 are supplied from the D.C. mains 2 through a resistance 21 and the coils 30, 130 through a resistance 31. For rectifier operation the coils 20 and 130 are energized, the circuit of coil 20 being completed through a closed contactor 29 on the switch 22 and the circuit of coil 130 being completed through closed contactors 119 and 28 on the switches 112 and 22. The moment of reversal of the connections of the discharge device 8, due to change in the voltages of the mains 1, 2, is determined by means of a polarized relay 39 in the circuit of the auxiliary device 103. This device will operate as an inverter, as the voltages alter and when the current rises above a predetermined minimum, the relay 39 operates closing the contacts 40, 42 to short-circuit the coil 20 and cause the switch 12 to open. The operating coil 30 is energized through contacts 19 and the switch 22 closes, completing the connections of the discharge device 8 for operation as an inverter. Closure of the switch 22 de-energizes the coil 130 so that switch 122 opens. Finally, the coil 120 is energized through contacts 129 and 18 causing closure of the siwtch 112 completing the connection of the discharge device 103 to the circuit as a rectifier. The grid circuit connection are altered by means of contacts on the various switches. By this arrangement the switches 112, 122 cannot operate until after the switches 12, 22 have operated. To change from inverter to rectifier connection the contacts 41, 42 close. To avoid hunting of the switches on starting of the installation, the switch 34 which completes the operating coil circuits is arranged so that one of its contacts 32, 33 closes before the other. In a modification, the converter 10 is a motor generator set.