GB841585A - Improvements in and relating to the control of electric motor-speed changing gear combinations - Google Patents

Abstract

841,585. Variable-speed control. BRITISH THOMSON-HOUSTON CO. Ltd. April 18, 1958 [April 18, 1957; Feb. 19, 1958], Nos. 12735/57 and 5442/58. Class 80 (2). [Also in Groups XXVII, XXIX and XXXV] An hydraulic or other variable-ratio gear 2 driven from a synchronous or asynchronous motor generator 1 for starting an aircraft gas-turbine engine 3 through reduction gear 18 and a one-way clutch 16, and subsequently being driven as a generator by the engine 3 directly through a one-way clutch 17, is controlled automatically according to the supply current when operating as a motor, to maintain substantially constant the output torque of the motor. In Fig. (Prov. 12735/57), the motor generator 1 has D.C. excitation s2, and its three-phase armature supply s1 passes in series through the stator winding of a power meter 4, the rotor winding of which is energized directly by the supply, whereby an arm 5 on the rotor, biased by a spring 6, moves in accordance with the power absorbed by the motor generator 1 and, through a control 8 adjusts the variableratio gear (which preferably includes zero output speed) to maintain a constant output torque of the motor generator 1, until the engine 3 drives whereupon the motor load becomes zero, the variable gear 2 moves to the end of its range and is subsequently controlled by a governor. In Fig. (Prov. 5442/58) the electrical power absorbed by the motor generator 1 is compared with that of a fixed reference supply 30, 31 and any deviation therefrom is used to operate the control 8 (such as a valve) of the variableratio gear 2 to maintain a constant output torque of the motor generator 1 during engine starting. Current and voltage transformers 23, 22 are used, the former supplying a fixed resistor 24, connecting a centre-tap of the transformer 22 to the junction of two transformers 25, 26 which feeds through bridge rectifiers 27, 28 a resistor 29 in circuit with the reference supply 30, 31. As the current in the resistor 29 rises above or falls below the reference current a polarized relay 210 or magnetic amplifier is actuated in the appropriate direction to operate the variable-ratio control 8 to adjust the motor load. Specification 814,217 is referred to.