Patent GB-190708020-A (GB)
Title: Improvements in Systems of Electric Motor Control.
Filed: 1907-04-05
Granted: 1908-03-26
Abstract: 8020. British Thomson-Houston Co., [General Electric Co.]. April 5. Motor control systems.-Relates to a multiple-unit system of control for electric motors, adapted to operate on both alternating and direct current, which is particularly applicable to electric railways having low-potential direct supply within town limits and high-potential alternating in less congested areas. Fig. 1 shows diagrammatically the equipment for a four-motor railway car, in which M' ... M<4> represent the motors ; T the collector or trolly ; S, S' main switches, the switch S closing automatically when the collector passes on to the alternating-current supply, and the switch S' when it is on the direct-current supply ; C a controller of the separately-actuated contact type : K, K<1> mastercontrollers ; E a magnetically-actuated commutating-switch for automatically connecting the field windings of each pair of motors in series for directcurrent working and in parallel for alternating- current working ; and RS a magnetically-actuated switch of a known type for reversing the motors. The controllers C on the various cars comprising the train are governed through the train-wires q<1> ... q<10> from any one of the master-controllers, and comprise switches 1, 2, 3 for connecting the motors to the trolly, a series switch 4, two parallel switches 5, 6, and switches 12 ... 15 for controlling the amount of the resistance in series with the motors ; these switches are all used for direct-current working. Switches 7 ... 11 are for alternating- current working, and serve to control the motors by connecting them to the different taps of the transformer N. The switches 12 ... 15 also serve the additional function of operating to prevent open or short-circuiting of the transformer during the shifting of the connexion from one tap to another. The relay U controls the circuits of the switches 7 ... 11 and, being only energized on alternating currents, cuts out these switches during directcurrent operation. On direct-current working, as the master-controller is turned toward the right, the switches 12 ... 15 are closed one after the other, causing the resistance to be cut out step by step. The next movement of the controller causes the series switch 4 to open and parallel switches 5, 6 to close. The motors are then connected in parallel to the line and in series with the resistance. The continued movement of the controller cuts out the resistance. Upon entering an alternating-current section, the transformer N is connected to the trolly, and the switches 1 ... 6 remain idle. The movement of the master-controller then operates the switches 7 ... 11, thus varying the connexion to the transformer as desired. The contacts on the master-controller are arranged so that the switch 8 is closed before switch 7 is opened, thus connecting, for an instant, the motors directly to the left-hand tap of the transformer through the switch 7, and to the second tap through the switch 8 and a section of the resistance. The connexion to the first tap is then broken and the resistance short-circuited by the consequent closing of the switch 12. In the same way, the voltage across the motors can be further increased up to the fifth tap without opening the motor circuit. Auxiliary motors M<5>, such as pump motors &c., may be also controlled, by the connexions shown, so as to operate on either current. The switches 7 ... 15 may be of the form described in Specification No. 3781, A.D. 1906.