Patent GB-936574-A (GB)
Title: Improvements in and relating to locomotive control systems
IPC: B60L15/32
Filed: 1962-07-02
Abstract: 936,574. Control of D.C. motors. GENERAL RAILWAY SIGNAL CO. July 2, 1962 [Aug. 24, 1961], No. 25230/62. Class 38 (3). [Also in Group XXXV] A train comprises main locomotive 6 and helper locomotive 8, a strain gauge 10 being connected to coupling 11. A system is provided for bringing the force exerted upon the coupling to zero or for maintaining the force at the coupling in either tension or compression so that the helper locomotive will afford a predetermined portion of the total tractive effort. When the strain gauge is subjected to no force there is no output from amplifier 16 to summing device 24. The output of unit 34, representing the speed of licomotive 8, causes pilot motor M54 to position potentiometers 54P1-54P4 in accordance with speed. A change of voltage across main traction generator 41 (Fig. 1A) causes relay R51 to operate motor M51 until potentiometer 51P1 is adjusted so that arms 65, 66 have the same potential, the position of arm 65 representing an analogue of the voltage across bus-bars 42, 43. Similarly, a positioning unit 52 is controlled by the voltage across resistor 125 which indicates the traction current. This current analogue is multiplied by the voltage analogue to obtain an indication of the horse-power developed by means of a circuit comprising potentiometers 51P2, 52P2, 53P1 and relay R53. When the voltage across this relay is balanced, arms 72, 73 are in positions representing the horse-power. A circuit comprising potentiometers 54P2, 55P1, 53P2 and relay R55 has the effect of dividing the horse-power by the speed to produce a torque signal. This voltage analogue of the torque is conducted by potentiometer 55P2 to summing device 24. The analogue of the torque as represented on potentiometer 56P2 is multiplied by the analogue of the speed on potentiometer 54P3 whereby potentiometers 57P2, 57P3 are positioned in accordance with the horse-power required. The position of arm 101 is determined by the positions of arms 88, 90 to select the proper throttle setting for the prime mover driving the traction generator. If the main locomotive applies more power, a tensile stress applied to coupling 11 causes strain gauge 10 to unbalance its bridge circuit, the output of which is amplified and smoothed before being delivered to summing device 24. Relay R56 is unbalanced and the potential across relay R57 changes so that arm 101 advances to increase the throttle setting until the locomotive 8 is pulling its share of the load. When the main locomotive is braked, the force upon coupling 11 is compressive causing a reverse potential from strain gauge 10 for application to the summing device 24. Switch 57S1 is moved to de-energize relay DBR so that control apparatus 40 is prepared for dynamic braking. Traction motors 45, 46 act as generators (Fig. 1C) connected to resistors 126, 127, the motor field windings 47, 48 being excited by the main generator 41. Potentiometer 57P3 controls the field of the generator. Potentiometers 58P1, 59P1 are positioned in accordance with the braking voltage and current, whilst potentiometer 61P1 indicates the brake horse-power. Potentiometer 60P2 applies a voltage indicating the braking torque to the summing device 24. This braking torque signal when summed with the strain signal balances the relay R56 whereby arm 90 of switch 57S1 still rests on the same quadrant. If the strain signal is increased, motor M57 operates arm 112 to increase the generator excitation so producing an additional braking horse-power output. The application of the brakes on the main locomotive causes the control apparatus 40 to return to the " idle " position. When the train starts the arm 101 will be placed in its maximum position, the unit 40 being controlled by speed-responsive filters 37, 38, 39, and associated relays 4R, 6R, 10R, so that as the train accelerates the next higher power wire leading to the unit 40 is energized. Each of these higher power wires provides more horsepower. When the train operates in a reverse direction, a relay 26 pole-changes the output from the strain gauge 10. The helper locomotive may be arranged to push those cars that are coupled in front of it, or the main locomotive may aid the helper locomotive in pulling the cars which are coupled thereto. In these circumstances there is normally either a compressive or tensile force on the coupling, and a biasing voltage is provided which opposes the output voltage from the strain gauge. This biasing voltage is obtained from potentiometers which are added to the unit 56 and its value is determined by the torque required of the helper locomotive. In another embodiment, the summing device 24 is provided with a voltage analogue of the horse-power instead of the torque. A plurality of lamps may be controlled by the arm 101 of switch 100 to serve as an indicator for manual adjustment of the various throttle and brake settings.