GB514310A - Improvements in contactor switches for controlling three phase electric current - Google Patents

Abstract

514,310. Electromagnetic contactor switches for three phase current. HEATON, F. May 2, 1938, No. 13007. [Classes 38 (iii) and 38 (v)] A contactor switch particularly suitable for changing from star to delta connection with a three - phase squirrel cage motor, comprises three switch arms A, B, C which are moved electromagnetically first to break one set of three phase circuits and then, after a pause, to close another set. In the form shown, the middle arm B carries a member b' which normally bridges two fixed contacts a<4>, c<4> connected to the pivoted points of the outer arms A, C so that the windings E, F, G of the motor are star connected. The switch is associated with another, somewhat similar main switch N, O, P adapted to connect the lines L', L<2>, L<3> to the other ends of the motor windings E, F, G. This occurs when a " start " button Q is depressed and the winding S<2> of the main switch N, O, P energized. Operation of the main switch also raises an arm T, Fig. 3, which compresses a spring t and so raises a rod t' under the action of retarding mechanism t<2>, causing the bridging of contacts V in the circuit to the electromagnet S<1> which then operates the switch A, B, C to break the star formation. The arms A, B, C are however prevented from moving their full distance to engage contacts J, K, M (and so effect delta connection) by a projection a<5> engaging a member t', until after a time interval this is moved out of engagement. The Provisional Specification refers to Specification 513,324.