Patent GB-190708079-A (GB)
Title: An Improved Method and Means for Controlling Electric Motors.
Inventor: LEONARD HARRY WARD
Filed: 1907-04-06
Granted: 1908-07-06
Abstract: 8079. Leonard, H. W. April 6. Dynamos and motors combined for transmitting power ; dynamos, driving and regulating ; motors, controlling.-The speed of electric motors, working under different loads, such as trains, is regulated by varying the pressure across the mains, by placing the generators supplying these mains first in parallel and finally in series. An alternating-current generator 1 supplies current to motors 2 driving direct-current generators 3<a>, 3<b>, 3<c>, and to a motor 2<a> driving an exciter 4. The exciter 4 is connected to the mains 5, 6 from which the fields of the propelling-motors are generated. The armatures of the generators and the propelling-motors are connected to leads 8, 9 through a controller, the circuits of the motor armature being provided with ammeters 12 and automatic cut-outs 13. The field magnets of the motors and of the generators may be provided with series winding. If the train is at rest and the circuits of the motors 2, 2, 2<a> are closed, these motors run on friction load while the controller is in its neutral position. When the controller is turned to its first 'on' position, the circuit of the exciter 4 is closed and the generators and propelling-motors are connected to the leads 8, 9 in parallel. The circuits of the field windings of the generators are provided with reversing-rheostats 7, and the strength of the current in the field windings of the motors is regulated by a reversing- rheostat 7<a> and rheostats 11. By a further rotation of the controller, the pressure between the mains 8, 9 is gradually increased (to the maximum voltage of each generator) and the train continues to accelerate. A further rotation of the controller weakens the fields of the generators 3<a>, 3<d> until they produce no current, when their armatures are disconnected from the lead 8, after which the fields may be reduced to zero. The disconnected armatures 3<c>, 3<d >are then connected through resistances to the conductors connecting the armatures 3<a>, 3<b> to the lead 9, after which these armatures are disconnected from the lead 9 and are replaced in series with the armatures 3<c>, 3<d> respectively across the leads 8, 9. The fields of the generators 3<c>, 3<d> are then gradually energized until the maximum voltage is reached. The next movement of the controller slightly weakens the fields of the generators 3<b>, 3<d> until they produce no current, after which they are disconnected from the lead 8 and their fields reduced until they generate no electromotive force. These generators being kept in series, they are then connected to the conductor connecting the generator 3<c> to the lead 9, after which all the generators are placed in series across the leads 8, 9 by disconnecting the generator 3<c> from the lead 9. The fields of the generators 3<b>, 3<d> are then energized until the maximum voltage is reached. To stop the train, the above operations are performed in the reverse order, when the energy of the moving load is transformed and fed to the line. To accelerate the train in the opposite direction, the field connexions of the generators are closed in the reverse direction by means of the reversing rheostats 7. In a modification, the fields of the generators may be grouped as shown in Fig. 11. The controller for performing the above operations may be provided with additional steps for obtaining a seriesparallel control of the propelling-motors. When the prime source of power 15, Fig. 14, is carried by the vehicle to be propelled, it is directly coupled to the armatures 16<a>, 16<b> of the generators. The propelling-motors are mounted at the wheels of the vehicle, and their armatures 19<a>, 19<b>, 19<c>, 19<a> are connected to the generators through a controller 21, by means of which they may be put n series or parallel according to the load conditions. The field windings of these motors are regulated by a reversible rheostat 22. When the line of contacts 24 comes into engagement with the line 25<a>, the armatures 16<a>, 16<b> of the generators is connected in parallel and the energy is conveyed to the motors by a, conductor 27, battery 18, or conductor 28, and controller 21. The field windings of the motors and generators are excited by the battery 18, which may also supply current for various other purposes. As the controller is moved to the position 25<b>, resistance is gradually cut out of the field circuits of the generators, thereby increasing the electromotive force supplied to the motors and so increasing their speed. Further movement of the controller weakens the field circuit of the generator 16<a>, and the armature of the generator will be disconnected and the field circuit further weakened until the electromotive force of the armature 16<a> is reduced to zero. The generators 16<a>, 16<b> are finally connected in series and the field 17<a> energized until the generator 16<a> produces its maximum electromotive force. When the controller is moved to the position 25<c>, resistance is gradually cut out of the motor fields, thereby causing a further increase of speed. The storage battery 18 may be used to start the engine 15 by moving the main controller to the position 25<b>, when the armature circuit of the generators will be closed through the motor armatures or through an adjustable resistance 32, while the field circuit of the motors-may be opened by the controller 22. The generators will then act as motors to start the engine until the latter begins to produce power, when the electromotive force produced by the generators will exceed that of the battery and the current will then flow for forward running. The main controller 23, controller 21, and switch 31 are preferably interlocked.