Patent GB-731519-A (GB)
Title: Improved dynamic brake system for electric locomotives
IPC: B60L7/04
Filed: 1953-12-11
Abstract: 731,519. Control of D.C. motors. GENERAL MOTORS CORPORATION. Dec. 11, 1953 [Feb. 25, 1953], No. 34508/53. Class 38 (3). In a traction system, a diesel engine E having a governor GOV drives a main generator G which is provided with series field winding SS, shunt field winding SH, and a battery-supplied winding BF controlled by a differentially-wound resistor LR. Traction motors M1-M4 are connected in parallel across the generator for driving the vehicle, the wiper arm 20 of the resistor LR being controlled by a vane motor 76 so that the power output of the generator conforms with that of the diesel engine for each throttle-position. For dynamic braking operation, the shunt field winding SH is disconnected from the power circuit, and is connected in parallel with the winding BF and in series with battery BAT and resistor LR, reversing switches S6, S7 being moved to the positions shown. Resistors R1-R4 are connected across the armatures of the motors M1-M4, and the motor field windings F1-F4 are connected in series across the armature of the main generator. Drum switches DR1, DR2 are moved to the braking position. Solenoid DEV of valve 84 is normally energized and solenoid INV of valve 80 de-energized, so that oil pressure is applied to each side of the vane 74 to maintain it in a stationary position. To increase the amount of dynamic braking, a push-button INC is actuated to energize the operating coil INV and the vane 74 is moved clockwise to decrease the value of resistor LR, so increasing the excitation of the traction motors. The magnitude of the applied dynamic braking is indicated by voltmeter VM. The degree of dynamic braking is decreased by depressing push-button DEC to de-energize the solenoids of valves 80, 84 and the vane motor 76 moves in the anti-clockwise direction. If the push-button INC is held depressed until maximum braking is achieved, the current is automatically limited. The voltage across resistor R3 is applied to relays BRA, BRR, and, when this voltage reaches a predetermined value, contacts C and L are disconnected to de-energize relay AMR. This de-energizes solenoid INV to halt movement of the vane 74 and energizes relay INMR. The solenoid INV is re-energized so allowing the dynamic braking to increase until the voltage across resistor R3 is sufficient to separate contacts T and Q of relay BRR and de-energize solenoid INV. If, due to change in locomotive speed, the voltage across resistor R3 increases still further, contacts T and Z of relay BRR are connected to energize relay DEMR and interrupt the circuit of solenoid DEV. The vane motor 76 moves in an anti-clockwise direction to decrease the excitation of the traction motors until the contacts T, Z are disconnected to halt the vane 74. If the relay DEMR fails to de-energize the solenoid DEV, the voltage across resistor R3 increases to a predetermined maximum. so that contacts C and H of relay BRA are connected to energize relay BWR and interrupt any energization circuit of the solenoid DEV. The vane 74 is then moved anti-clockwise until contacts C, H and T, Z are disconnected. A number of locomotives having similar braking systems may be arranged so that the dynamic braking for each unit is controlled from a leading unit, train lines FC, DBC, N in the leading unit being coupled to lines FC', DBC<SP>1</SP>, N<SP>1</SP> in the trailing unit. If increased dynamic braking is required in both the leading and trailing units, the push-button INC of the leading unit is depressed, so moving the arm 20 clockwise. Current flows from the arm 20 to arm 20<SP>1</SP> to energize relay INMR<SP>1</SP> which closes a circuit through solenoid INV<SP>1</SP> of valve 80<SP>1</SP>. The vane 74<SP>1</SP> of the vane motor 76<SP>1</SP> is then moved until the resistance LR<SP>1</SP> in series with the generator field windings SH<SP>1</SP>, BF<SP>1</SP> is the same as resistor LR in circuit with the windings SH, BF, whereupon the circuit through the coil of relay INMR<SP>1</SP> is discontinued. If the resistance of the regulator LR is greater than that of the regulator LR<SP>1</SP>, current passes from arm 20<SP>1</SP> to the arm 20 and relay DEMR<SP>1</SP> is energized. The solenoid DEV' of valve 84<SP>1</SP> is de-energized and the arm 20<SP>1</SP> is moved to correspond with the position of the arm 20. The voltage-sensitive relays BRA<SP>1</SP>, BRR<SP>1</SP> operate in the same manner as the relays BRA, BRR. When the voltage across resistor R3' exceeds a predetermined amount, automatic braking current control is instituted in the trailing unit and further manual control of the trailing unit by the push-buttons in the leading unit is prevented. The control position can be changed from one locomotive to the other by moving drum switches DR1, DR2 to the " off " position and switches DR3, DR4 to the " braking " position.