Patent GB-190400716-A (GB)
Title: Improvements in and relating to the Control and Propulsion of Vehicles Propelled by Electric Motors.
Inventor: RAWORTH JOHN SMITH
Filed: 1904-01-11
Granted: 1904-12-31
Abstract: 716. Raworth, J. S. Jan 11. Motors, controlling. -Relates to the control and propulsion of vehicles propelled by electric motors, more particularly motors having two circuits and controlled by controllers of the kind described in Specifications Nos. 3657, 3658, and 10,723, A.D. 1903. Fig. 1 shows a diagram of the wiring of an electric tramcar having controllers A, B at opposite ends. These controllers have speed levers d which move over bars c, and resistance contacts c<1> ... c<16> to vary the resistance in circuit with the shunt field windings, and power levers h which move over bars k and contacts l<1> ... l<5> to govern the armature circuit. The levers d, h are interlocked by a pin s on the lever d engaging slots t, u, v in a plate q formed on the lever h, so that the armature circuit can only be made and broken when the speed lever is in the position of maximum field excitation. Each controller is connected with the trolley f bv leads g, which run fore and aft of the vehicle and are connected with contacts c<1>, l<5> as shown. Contacts e<2> connected to the bars e, and contacts c<18> connected to earth at E, are provided. The speed lever d of the controller not in operation, e.g., B, is locked on these contacts, the power lever h simultaneously resting on dead contacts K<3>, l<8>. The power lever is so arranged that, after breaking both positive and negative connections, it closes the armature circuit through a resistance p by means of a pair of contacts k<2>, l<7> and leads m, l, one side of the resistance being connected to earth E through the lead E'. The armatures a have special series windings w, in addition to the shunt winding b, which can be placed in circuit between the armatures and earth by bringing contacts X, carried by the speed levers, between the contacts 7, 3 on the leads 1, 5. To permit the speed lever d to be pulled back, after the power circuit has been broken and the emergency circuit closed, to bring the contacts X into the required position, the slot t is extended at t<2>. Or the series windings may be brought into action by means of a switch located in the controller casing and operated by the speed lever ; or they may be arranged to be brought into action each time the braking-circuit is closed. The speed of the vehicle is controlled by increasing or decreasing the field strength, the motors, when the speed is being decreased by increasing the field strength, acting as generators returning current to line and producing a retarding effect. When the speed lever d is drawn on to the contacts e, c', the power lever h is released, and is forced by a spring on to the contacts k<2>, l<7>, thus short-circuiting the armatures through the resistance p and setting up a powerful braking action. Should the electric energy fail, the speed lever is drawn back to bring the series windings into operation. For automatically controlling the ratio of the field current to the armature current, so that acceleration may be within the maximum safe limit, a checking-device is applied to each controller. One form of checking-device is shown in Fig. 6, consisting of a pair of solenoids S, S' having cores S<2>, S<3> connected by links to the speed lever d. The solenoid windings are connected, respectively, in series with the armatures a and shunt field windings b, and the number of turns is so arranged that the effect is nil when the ratio of the two currents is at or near the maximum. Or the windings may be similar and the solenoids operated as a relay governed by two other solenoids. Fig. 7 shows a modification of the device shown in Specification No. 10,723, A.D. 1903, in which a tubular armature U connected to the speed lever d by a link T is acted on by an electromagnet W controlled by a relay operated by balanced solenoids. The electromagnet may actuate a pawl to engage teeth on a rod carried by the speed lever. Another part of the invention relates to devices for changing the motor connections from series to parallel, and vice versÔ. The operating-lever for this device is preferably pivoted on the pivot of the power lever, and is normally held by a spring in the series position, a stud or projection preventing this lever from being operated in advance of the power lever. The controllers are also provided with means for augmenting or decreasing the field strength when the motors are changed from series to parallel, and vice versß. Figs. 9 and 10 show two views, from opposite sides, of a series-paralleling arrangement. A bar 20 carries a solid contact 21 and a pair of contacts 22, 23, with which a pair of pivoted arms 24, 25, acted on by an electromagnet 27 and connected with the armatures a, make contact. When the arms are both on the contact 21, the armatures are in saries, but, when they are on the contacts 22, 23, the armatures are in parallel, the arms being held in this position so long as the magnet 27, which is in series with the armatures a, remains energized. When the lever arms are moved from the series to the parallel position, a circuit is closed by a spring contact 28 and a pivoted contact 29 direct from the line through the shunt windings. When the arms are moved in the reverse direction, the field is weakened by placing the line to earth through the series windings w in a direction to demagnetize the fields. This is effected through the spring contact 40, pivoted contact 39, and three contacts 34, 35, 36 carried by the bar 20, the contact 35 being connected to line and the contact 34, 36 to one side of the field windings w. In applying the invention to tramcars, trains, automobiles, and other vehicles intended to work always in one direction, the controllers are modified so that all the contacts for forward or backward motion are contained in one controller. Fig. 11<a> shows the wiring of a controller for an automobile. A lead 14 connects the speed and power levers d, h to a battery f<1>. The power side of the controller is provided with an extra contact l<9>, and the power lever h is linked to a switch lever l<10> moving over contacts l<12>, l<13>. When the car has been brought to rest by the power lever coming on to the braking-contact l<7>, its motion may be reversed by pulling the power lever back on to the contact l<9>, which also moves the lever l<10> on to the contact l<15>, and thus reverses the current through the armatures a. To allow the further movement of the power lever, the slot u in the plate q is extended beyond the slot t. The speed lever may be fitted with a pawl or catch, which, when the field is on, works between stops on the controller cover situated in positions of maximum and minimum field excitation. To move the lever beyond the stops, the pawl must be depressed.