Patent GB-676271-A (GB)
Title: Improved electro-motive traction systems
IPC: H02P9/08
Filed: 1950-08-15
Abstract: 676,271. Control of D.C. motors. GENERAL MOTORS CORPORATION. Aug. 15, 1950. [Aug. 17, 1949] No. 20200/50. Class 38 (iii). [Also in Group XXXV] Relates to an electro-motive traction system for locomotives comprising an engine, an electric generator driven thereby, and a plurality of electric motors supplied from the generator. An engine speed-responsive device controls the fuel supplied to the engine and is additionally manually variable, a rheostat, which controls the field excitation of the generator and which is variable conjointly by the fuel supply control and by the manual control, being connectable with resistors in response to the manual control when the rheostat is varied from a low to a high excitation position in order to obtain a more prompt increase in power output. As shown, a Diesel engine E, drives a generator G, which supplies series traction motors M1, M2. M3, M4, and has a series field winding S, a shunt field winding SH, and a separatelyexcited field winding BF which is energized from a battery BAT. An engine-driven governor GOV, controls the engine fuel regulator F, and also a rheostat FR, in the circuit of the generator field winding BF. Initially the engine operates at idling speed and contactors S13, S24, are closed so that the motors are connected in multiple series across the generator. The winding of the valve ORV, is also energized so that a vane motor 213, drives the arm of the rheostat FR to the maximum-resistance position and causes field switch FS, to occupy its upper position. When a master controller MC, is moved to a first starting position the field winding BF, is excited. The winding of the valve ORV, is de-energized so that the rheostat FR, begins to move towards its minimum resistance position. Upon moving the master controller to its second starting notch the windings of valve AV, and switch AS are energized so that an electro-pneumatic governorspeed and load-setting device SL, causes slight upward movement of link 153, thereby setting a pilot valve 209, for decreased resistance of the rheostat FR. The increased loading of spring 143, moves pilot valve 133, to cause oil under pressure to lift power piston 169, so increasing the setting of an engine fuel regulator lever F. The engine-driven centrifugal device 141, returns the pilot valve 133, and sleeve 135, to their original positions when the plant operates at the set speed and load, so leaving the engine fuel lever and field rheostat in the new controlling positions. Closure of switch AS, connects a resistor R1, across rheostat FR, to produce a quicker increase in the generator field excitation than can be accomplished by movement of the field rheostat, in order to afford a more prompt increase of power output. Further movement of the master controller progressively increases the speed and load setting of the governor GOV, through regulation of the valves AV, BV, CV, DV, of the device SL. At the same time, the rheostat FR, is progressively shunted by resistors R1, R2, R3. When the locomotive accelerates to a speed sufficient to cause movement of the field rheostat to its mid-position, the switch FS, is moved to its lower position to excite the generator shunt field winding SH, in combination with the winding BF, and to remove the shunting resistors R1, R2, R3. Such movement of the switch FS momentarily disconnects the generator field winding BF, which is discharged through resistor BDR. The valve ORV is energized to move the field rheostat FR, towards its maximum-resistance position. Immediately thereafter the field winding BF, is re-connected, the field rheostat moved towards the higher excitation position, and the shunt field winding SH, is placed in circuit. When the arm of the rheostat FR, is moved to its minimum-resistance position a switch FTS, is actuated to cause transition of the traction motors to parallel connection with the generator. Closure of switch FTS, disconnects the field windings SH, and BF, and causes the rheostat FR, to be moved to its maximum-resistance position. A relay VT, affords a time-delay sufficient for the generator field windings to discharge and for movement of the rheostat FR, back to its maximum-resistance position. The motors are then connected in parallel across the generator, field windings are re-connected and the rheostat FR, moved back to its original position. Backward transition of the motors is effected in a similar manner by means of relay BTR, which changes the motors from parallel to multiple series connection in response to a given value of motor current or movement of the controller to an idling position. When contacts of a reply WSR, close due to wheel slippage the generator field windings are discharged and the rheostat FR, is moved to its maximum resistance position.