GB189925453A - Improvements in Alternating Electric Current Motor Systems. - Google Patents

Abstract

25,453. British Thomson-Houston Co., [Davis, A. G.]. Dec. 22. Switches.-Relates to alternating-current motor systems, particularly those of the tandem and tandem-multiple types, the object being to enable the motors to be started with full torque and to run efficiently at various speeds when supplied from a source of single-phase currents. A single-phase motor, started by an auxiliary motor of the splitphase type, is conrected in tandem to a polyphase motor driving the same load, e.g., a street car. By means of a controlling-switch, the resistance of the secondary circuit of one or both of the motors is varied, the phase displacement in the intermediate circuits is neutralized or adjusted, and the motors are ultimately ioined in multiple with the singlephase mains. Fig. 1 is a diagram of the system, in which A represents a single-phase motor, B a polyphase motor, and K the controlling-switch with its contact-cylinder developed. In the position 1 of the controller, an auxiliary motor M of the split-phase type is connected with the single-phase mains and rotates a " flux screen " A<3> in the space between the primary and secondary members of the motor A for the purpose of starting the latter. When the controller is moved to the position 2, the primary winding of the motor A is connected to the single-phase mains, and its secondary winding to the primary of the motor B through single sections of condensers C, C', the secondary of the motor B being short-circuited through resistances R', R<2>. The motors now run at a low speed. Tn the position 3 of the controller, the auxiliary motor is cut out, another section of each condenser is connected to the intermediate circuits, and the resistances R, R<2> are cut out. This results in an increase of speed. In the position 4, all the sections of the condensers C, C<1> are thrown in, and the secondary winding of the motor B is short-circuited in small sections by a movable ring under the action of an electromagnet M<b>. The motors now run at nearly half the synchronous speed. Tn the position 5, the secondary winding of the motor A is shortcircuited in small sections by the action of a second electromagnet M<a>, and, in the position 6, the intermediate circuits are opened. In the position 7, the two motors are connected in multiple, their secondaries being short-circuited through resistances R<1>, R' and R<3>, R<4> respectively. In the position 8, the resistances are cut out, and, finally, in the position 9, both secondaries are short-circuited in small sections by the magnets M<a>, M<b>. The motors now run at a speed very near synchronism.