GB626247A - Systems for controlling the connection of a load across a direct current motor supplied through a rectifier - Google Patents

Abstract

626,247. Control of D.C. motors. BRITISH THOMSON-HOUSTON CO., Ltd. May 1, 1947, No. 11692 Convention date, May 1, 1946. [Class 38(iii)] In a system in which a D.C. motor is supplied through a rectifier, a resistance is arranged for connection across the load by an overload voltage relay also connected across the load, there being an arrangement whereby upon cessation of regeneration the overvoltage relay is reset and its connections restored to normal while the resistance is connected across the load. When a regenerative voltage is attained by a motor 6 supplied through a rectifier 1, the consequent energization of an overvoltage relay 9, energizes, through its contacts 10, a relay 8 whereby a resistance 7 is connected through contacts 20 across the motor, while contacts 21 are also closed. Upon increase of current from rectifier 1 to motor 6, a current relay 11 closes its contacts 12 at a predetermined current, and a time relay 13 is energized. This momentarily closes contact 14 and energizes an auxiliary control relay 15 which through contacts 16 energizes relay 17 and breaks at contacts 19 the energization circuit of overvoltage relay 9, but through contacts 18 maintains relay 8 energized. When contacts 14 open, relay 17 is de-energized thus resetting overvoltage relay 9 for immediate use, but relay 15 does not open until after a further time delay, when the opening of contacts 18 de-energizes relay 8 to disconnect resistance 7 from the motor circuit.