GB596892A - Improvements in and relating to the control of engine-driven electric generating plant - Google Patents

Abstract

596,892. Automatic control systems for generators. ENGLISH ELECTRIC CO., Ltd., and SPAINK, J. H. ABBINK-. Aug. 3, 1945, No. 20009. [Class 38 (iv)] In an automatic speed control arrangement for an engine-driven generator supplying a varying load, e.g. traction motor, the generator excitation is controlled by a switch arranged to open or close in response to deviations of engine speed from a datum and is arranged to be varied gradually in the corrective sense in response to the switch operation. The generator 1 supplying traction motors 2 and 3 has shunt field la and separately excited and mutually assisting fields 1b and 1c connected across the D.C. supply 4. At load currents up to that corresponding to the maximum rated engine output at full fuel supply the governor 7 maintains the switch 6 closed, thus energizing the field 1c and the associated dynamo-electric machine 8. The latter operates as a motor and drives the flywheel 9. With an increase in the load of generator 1 above the maximum the switch 6 is opened by governor 7, consequent upon a fall in engine speed, and the field 1c is disconnected from the source 4 but still energized from machine 8, now operating as a dynamo, at a rate decreasing gradually as the kinetic energy of the flywheel 9 and armature of 8 is absorbed. Conversely should the load in generator 1 now be reduced, the switch 6 will be closed but the excitation of field 1c will rise gradually at a rate depending on the voltage developed across machine 8, now operating again as a motor, which in turn depends on the increase in speed of 8 and thus on the combined inertia of flywheel 9 and armature 8. The governor 7 may be an auxiliary one or may be the main control governor and in a modification, the damping of the rate of change of current in the field winding may alternatively be produced by means of a variable resistor in series, with the field, controlled electrically or hydraulically by the governor. According to the Provisional Specification the governing control is exercised through the field circuit of the generator exciter.