GB578494A - Improvements relating to the control of direct current generators - Google Patents

Abstract

578,494. Transmitting mechanical power. BRITISH THOMSON-HOUSTON CO., Ltd., MAGGS, A. H.; and ADKINS, B. July 27, 1944, No. 13126. [Class 38 (iv)] A control system for maintaining constant the reaction torque of a D.C. generator over a range of speeds, comprises a torque motor or wattmeter loaded with a substantially constant torque, the potential element of which is supplied through a choke and rectifier from alternating current, the voltage of which is proportional to the generator voltage and the frequency of which is proportional to the speed of the generator, the current element of the wattmeter being excited in proportion to the load current of the generator. As shown, the alternating current is derived from separate windings 2, which may be single phase or polyphase, on the generator armature. The reactance of the choke 9 is high compared with its resistance. The current element 12 of the torque motor 11 may carry the generator current or a part of it as shown. The torque motor is loaded by means of a hanging weight 15 or alternatively by means of a coiled spring and is shown directly coupled to an arm 8 of the rheostat 7. The torque exerted by the motor 11 is proportional to the reaction torque of the generator. The motor may operate a rheostat in the field circuit of an exciter or a switching means for a rheostat operating motor. The torque motor may be damped, preferably by electro-magnetic means. The alternating current may be derived from the generator armature winding itself, suitably tapped or from a separate alternator driven at a speed and excited proportionally to the D.C. generator. Alternatively it may be derived from an armature excited inverter driven at a speed proportional to that of the generator and connected to its terminals.