GB718141A - Improvements in or relating to variable speed electric drive systems - Google Patents

Abstract

718,141. Control of D.C. motors. GENERAL ELECTRIC CO., Ltd., and SCOTT, P. June 15. 1953 [April 17, 1952]. No. 9706/52. Class 38(3) [Also in Group XXXV] To maintain substantially constant horsepower, in a variable speed electric drive system for e.g. a a diesel electric ship or train comprising tour generators G1.4 supplying two motors PM, SM with, all the armatures connected in series in a closed loop (i) the excitation of the generators is controlled to maintain constant current in the loop. and (ii) the excitation of each motor is controlled to maintain constant armature voltage, for a given setting of the controller. Constant current. The generator fields are supplied from a common exciter E having its fields EF2. EF1, energized in accordance with the loop current, and the setting one of the controllers PC, SC, which has the greater value, as described in Specification 681,732. Constant voltage. The control system for each motor is identical.. Considering motor PM, the field PMF is supplied from an exciter EM1 energized from a pilot exciter PE1 having its fields PF2, PF1, fed from the motor armature and a reference voltage determined by the controller PC. Further features: -(i) Limiting acceleration: when the exciter voltage exceeds that of the reference voltage supply CV field PF3 is energized through rectifier X2. (ii) Speed limiting: when the voltage of the tachometer generator TP (driven by the motor) exceeds the voltage CV field PF3 is energized through, rectifier X1. (iii) Resistances RG1-4 may be shortcircuited by auxiliary contacts on the isolating switches S to compensate for reduced output available when a generator is removed from the loop.