Patent GB-764367-A (GB)
Title: Improved electro-motive traction control system
IPC: B60L3/10
Filed: 1955-02-07
Abstract: 764,367. Control of D.C. motors. GENERAL MOTORS CORPORATION. Feb. 7, 1955 [April 7. 1954], No. 3590/55. Class 38(3) In an electro-motive traction system having means for checking the slippage of the traction wheels driven separately by the traction motors, an engine E drives a main generator G provided with a battery-energized field winding BF as well as shunt and series field windings SH and DF, CF, IF. A governor GOV in combination with regulator FR controls the excitation of the field winding BF. The series traction motors M1-M4 can be connected as pairs in series by closure of contactors S14, S23, or singly in parallel by means of contactors P1-P4. The circuits of motors M1, M4, both include opposing current windings of wheel-slip relays WS1, WS4, and the circuits of motors M2, M3, both extend through windings of similar relays WS2, WS3, the relays being responsive to unbalance of the motor currents. The vehicle is started by closing switches BS, CS1, and S so that the series contactors are closed, relay SHR being energized to shunt resistor SD from the generator shunt field circuit and to operate relay BR. This opens the circuit through the governor over-ride solenoid ORS and connects the winding BF to the battery BAT. The mid-points of balance resistors R1, R4 and R2, R3, are connected in bridge circuits through bias coils C4, C3, of relays WS4, WS3, to points between the motors M4, M1, and M2, M3, respectively. If the wheels of either motor Ml or M4 should slip the bridge circuit is unbalanced and current flows through coil C4 to energize the relays WS4 and WSCR. This causes, firstly, shunting, of the field winding BF, and, after a time delay, disconnection of this winding the flux of which gradually decays to reduce generator power and eliminate wheel-slip. The solenoid ORS is also energized to allow the field regulator FR to move towards its minimum position, and the resistor SR6 is inserted in series with the field winding SH. If the wheels of either motor M2 or M3 slip, bias coil C3 is energized to operate relays WS3, WSCR, in a similar manner. The motors are connected in parallel by opening switch S and closing switch P, the bias coils C1, C4, and C2, C3, being connected as pairs in series across the generator. If the wheels of the motor 4 slip, for example, the excitation of one of the current-responsive windings of the relay WS4 decreases, and the bias coil C4 acts with the effect of the fall of current to operate the relay. If the wheels of the motor M1 slip, the bias coil C4 acts against the effect of the fall of current through the motor M1 so that the relay WS4 does not operate, a separate relay thus being necessary for each motor. By the use of the bias coils, the effect of which increases as the generator-voltage rises and the motor-currents decrease, the sensitivity of the wheel-slip relays to difference in the motor speeds can be maintained. False operation of the wheel-slip relays may be caused by mechanical vibration of the motors which leads to variation of back-electromotive force. To prevent this, the current-responsive windings of the relays are connected in series with the field windings of the motors the high inductance of which resists any sudden changes of the motor-currents. Tapped portions T8, T9, of calibration resistors R8, R9, are short-circuited upon closure of swtches SW1-SW4 to increase the excitation of the bias coils and to off-set the loss of sensitivity of the wheel-slip relays when the motor fields are shunted.