Patent GB-190907114-A (GB)
Title: Improvements in and relating to Electric Motor Control.
IPC: B60L9/26
Filed: 1909-03-24
Granted: 1910-03-17
Abstract: 7114. British Thomson-Houston Co., [General Electric Co.]. March 24. Master control systems; systems for alternating current motors only.-A controller for alternating-current commutator motors short-circuits the armatures and then varies the motor connexions. In the high-speed position, the armature shortcircuit is broken and is not again completed as the controller returns to its initial position. Means are provided to limit the motor speed. The motors are supplied from the secondary of the transformer D, and the middle point of the winding is connected to earth. The m o t o r connexions are varied by electro - magnetic switches G ... G<6>, some of which carry interlocking contacts to ensure the proper sequence of operation. When the master controller H is moved to its first running position on the line 2, a current flows from the transformer through contacts h<1>, h<8>, actuating-winding G<4>, upper contact g<5>, lower contact g<3>, and contacts h<10>, h<11> back to the transformer. Another current flows through contacts h<1>, h9, actuating-winding G, and contacts h<10>, h<11>. The switch G<4> closes and short-circuits the motor armatures A, and the switch G connects the motors to an intermediate point on the transformer D through the resistance E. The actuating-winding of a switch G<7> is connected across the exciting- windings B of the motors, and this switch now connects the actuating-windings to the right-hand side of the transformer independently of the master controller. When the master controller is moved into position 3, the switch G<6> closes and short-circuits the resistance E. In position 4, transitional connexions are established, and the resistance E is inserted in the circuit. As the controller passes from position 4 to position 6, the switch G<1> closes and connects the winding C to the transformer as shown in Fig. 5. The switch G then opens and disconnects the resistance E. Further movement of the controller breaks the maintaining-circuit of the switch G<4>, which then drops and breaks the armature short - circuit. Higher speeds are obtained by varying the transformer connexions. If the speed of the motors rises excessively when the controller is left in position 6, the voltage on the exciting-windings B drops and the switch G<7> opens. This disconnects the actuating-windings of the switches from the right-hand side of the transformer, and the switches then open the motor circuit. The circuit is completed again when the controller is moved back to the starting position or into the first high-speed position. In either of these positions the actuating - circuits are completed through contacts h<10>, h<11> independently of the switch G<7>. In position 8, the switch G<2> is actuated and connects the junction of the windings B, C to the transformer through the resistance F. The switch G<4> drops and completes the actuating-circuit of switch G<5>, which then short-circuits the resistance F, giving the connexions shown in Fig. 8. Further movement of the controller varies the electromotive force impressed on the armature. Specifications 17,474/07, [Class 35, Dynamo-electric generators &c.], and 6963/08 are referred to.