GB427442A - Electric motor control and braking systems - Google Patents

Abstract

427,442. Control of D.C. motors; controllers. ENGLISH ELECTRIC CO., Ltd., 28, Kingsway, London, ANDREWS, H. H., Phoenix Works, Bradford, Yorkshire, CONSTANT, P., 28, Kingsway, London, and MARDIS, P. L., Phoenix Works, Bradford, Yorkshire. Jan. 17, 1934, No. 1692. [Class 38 (iii)] A controller for a traction motor, which is biassed to an " off " position and controls power and regenerative braking circuits when moved to one side of that position, and rheostatic braking circuits when moved to the other side, is actuated by a single pedal which is rocked to one side of the " off " position by toe pressure and to the other side by heel pressure. The circuit connections are shown in Fig. 1, in which 5 is the motor armature, 6 a reversing switch, and 4 and 7 are series and shunt field windings, respectively in series with resistances 3, 8. The controller 10 is shown in the " off " position, and comprises fixed contact fingers c1 ... c12 and co-operating segments 10a. To start the motor, the controller is moved by toe pressure to the position P1, thereby energizing the windings In, lp of the line contactors LN, LP, the windings f 1 ... f3 of the contactors F1 ... F3, which short-circuits the shunt field resistance 8, and the winding f4 which opens the switch F4 and disconnects a discharge resistance 9 in shunt with the shunt winding 7. The controller is then moved successively to the positions P2 ... P5, to energize the windings rl ... r4 of contactors R1 ... R4 and cut out the series resistance 3. The last contactor R4 short-circuits the positive line contactor LP, opens the energizing circuits of the latter and of the contactors R1 ... R3 by opening its contacts r41 and closes a holding circuit for itself at its contacts r42. It also prepares a circuit at its contacts r43 for the winding tr of a brake-transition relay. Further movement of the controller through the positions P6 ... P8 releases the contactors F1 ... F3 and inserts the resistance 8 in series with the shunt field winding 7. Backward movement of the controller from the position P8 to P5 reinserts the resistance 8 for regenerative braking. If it is desired to pass smoothly to rheostatic braking, a switch BS is closed by slight depression of the mechanical brake pedal, before the controller reaches the position P1. When the controller reaches this position, the winding tr is energized, and this in turn closes the winding b of the rheostatic brake contactor B through its contacts TR3. The contactor B opens the energizing circuit of the contactor R4 at contacts bl and disconnects the motor armature from the line and connects it across the resistance 3 for rheostatic braking. If the transition relay is not used, the contactor B can be closed by moving the controller by heel pressure to the position B1. Successive movements to the positions B2 ... B4 cut out the resistance 3 to increase the braking effect. The actuating mechanism for the controller is shown in Fig. 2. The operating pedal 11 is pivoted at 12 to a bracket 13 on a base plate 42, and is connected by a rod 15, bell-crank lever 25a, 25b and rod 32 to the controller 10. Springs 17, 20 surrounding the rod 15 on each side of a fixed bracket 27, normally bias the controller to the "off" position. The auxiliary brake switch BS is normally held open by a bell-crank lever 36 connected by a rod 38 to a crank 39 secured to the mechanical brake pedal 40. Initial movement of this pedal rocks the bell-crank lever 36 and allows the switch BS to close.