GB587325A - Improvements in control systems for electric power plants - Google Patents

Abstract

587,325. Automatic control systems transmitting mechanical power. BRITISH THOMSON-HOUSTON CO., Ltd., and LEWIS, T. X. Nov. 17, 1944, No. 22873. [Class 38 (iv)] Speed.-The load on the prime mover driving a generator supplying a motor is controlled to maintain constant speed of the prime mover by an A.C. voltage varying in frequency with the speed and fed to a resonant circuit; any change of current or voltage in that circuit is caused after rectification to vary the generator excitation in a corrective sense. As shown, the field winding 9 of a cross-armature reaction excited generator 7 supplying the shunt field 2 of the main generator 1 is energized in accordance with the difference between rectified voltages obtained from an inductance 13 and a condenser 14 in a series resonant circuit loading a tachometer alternator 3, with or without a frequency multiplier 4. The machine 7 has a stabilizing field winding 8 and a currentlimitiiig winding 6 in series with a resistance 17 which may have a negative volt-ampere characteristic, e.g. as described in Specification 292,110, [Class 38 (iv)]. The governor loading means 16 may be adapted to' change the resonance characteristic of the control, e.g. as indicated. Modified arrangements referred to include a parallel resonant circuit, a pilot-motor driven rheostat controlling the generator field and responsive to polarized relays or the equivalent, and alternative source of A.C. varying with prime mover speed. Specifications 146,136 and 284,316, [both in Class 38 (iv)], also are referred to.