Patent GB-700092-A (GB)
Title: Improvements in and relating to gas turbine-electric power plants
IPC: B60L50/10
Filed: 1950-03-20
Abstract: 700,092. Automatic control systems for gas turbines; transmitting mechanical power. BRITISH THOMSON-HOUSTON CO., Ltd. March 20, 1950 [March 30, 1949], No. 6882/50. Class 38 (4) In a gas turbine-electric system for vehicle propulsion a manual speed setting device and electric means automatically responsive to turbine speed, control both the electric generator and the fuel supply to the gas turbine, means being provided for limiting generator excitation and for limiting the maximum rate of fuel supply in dependence upon the temperature of the air supplied to the gas turbine. In a gas turbineelectric power unit for a locomotive, Fig. 1, the gas turbine 15 drives, through gearing 22, a main generator 23 supplying traction motors 42 43. The turbine also drives an axial flow compressor 13 and an oil fuel pump 21 supplying air and fuel respectively to combustion chambers 14, a pump 20 supplying oil for control purposes, a tachometer alternator 18 for automatic speed control, and a governor 19 which closes solenoid-operated valves 27, 29 to cut off the supply of fuel and control oil from tanks 28a-c when turbine speed exceeds a predetermined value. The output of tachometer alternator 18 energizes, through rectifiers 100, a winding 96 of a solenoid-operated valve 93 controlling an oil servomotor 88 engaging at 91 a floating beam 60 attached to a valve 84 controlling the pressure in a pipe 81. Turbine speed variations thus vary the pressure in pipe 81 which controls a wobble plate (not shown) to vary the output of fuel pump 21 in the desired sense to correct the speed variations. An additional winding 97 on control valve 93, energized through a condenser 97a in response to rate of movement of a potentiometer 98 by servomotor 88 and in response to rate of change of main generator current through a transformer 102, serves to reduce hunting. Servomotor 88 also operates, through gearing 90a, a rheostat 44 which over part of its range of movement controls the energization of a control field winding 38 of an amplidyne exciter 35 supplying field winding 34 of generator 32 so that load on the turbine is reduced in order to maintain speed. Manual speed setting is effected by a throttle lever (not shown) operating ganged potentiometers 56, 80 in the locomotive cabin. Movement of potentiometer 80 energizes oppositely wound D.C. windings of magnetic amplifiers 73, 74 the outputs of which are then unbalanced and, being rectified and respectively associated with reverse field windings 70, 71 of a D.C. motor 63, motor 63 runs to drive a potentiometer 78, forming a bridge circuit with potentiometer 80, until the input to magnetic amplifiers is again zero. Motor 63 drives a cam 65 which, through a rod 66 engages beam 60 to control valve 84 and thereby adjust the fuel supply to obtain a turbine speed corresponding to the new setting of the throttle lever, which is thereafter maintained automatically by tachometer alternator 18. Motor 63 also drives a potentiometer 99 controlling the energization of winding 96 of valve 93 to provide further control of fuel supply and generator loading. Motor 63 further adjusts the setting of governor 19 in accordance with throttle lever position. These two last mentioned functions of motor 63 are prevented when the fuel supply reaches a predetermined maximum or minimum value by a lost motion coupling, Fig. 2 (not shown), associated with motor 63. The minimum value is fixed but the maximum value is varied automatically with inlet air temperature so that maximum turbine speed is reduced at lower temperatures. Movement of potentiometer 56 by the throttle lever controls the energisation of the saturating windings of one of each of two pairs of saturable reactors 50, the A.C. windings of each pair forming potential dividers across A.C. sources 55, 55a to energize through rectifiers 52, 53 control field winding 38 of exciter 35. The other saturating winding 58 of one pair of saturable reactors 50 is energized in accordance with the current in main generator field winding 34, while the other saturating winding 59 of the other pair is energized in accordance with the main generator current so that both generator field and armature currents are maintained at a value detemined by the throttle lever setting. In Fig. 2 (not shown) an additional control beam of the type described in Specification 680,209, [Group XXIX], applies a vertical force to end 61 of beam 60 to limit the maximum value and rate of change of turbine exhaust gas temperature.