GB473787A - Improvements in or relating to electric controllers - Google Patents

Abstract

473,787. Master control of motors. IGRANIC ELECTRIC CO., Ltd. July 10, 1936, No. 19153. Convention date, Sept. 6, 1935. [Class 38 (iii)] An electric control system includes means for effecting an operation of a switch and a device for delaying the operation, the device comprising a coil and means to energize the coil to prevent the operation of the switch, and to subject the coil to a reverse voltage, whereby, after a time interval depending upon the inherent inertia in the circuit of the coil, the operation of the switch is permitted. Upon operation of a start switch 4, Fig. 1, a main switch 2 is energized and the motor 1 connected across the supply, the operating coil 3a of an accelerating contactor 3 also being energized but the contactor prevented from operating by the energization of a coil 3b connected across the supply between a resistance R1 and a resistance R of lower ohmic value. The main switch maintains itself over contacts 2a and at contacts 2b completes a circuit from the supply through a comparatively high resistance h2 to reverse the energization of the coil 3b. The magnetic flux of the coil 3b is thus reduced and made to pass through zero and the switch 3 is then operated to short-circuit accelerating resistance r. The reverse circuit for the coil 3b completed by the contacts 2b may be supplied from a tapping on the accelerating resistance r. In a modification, Fig. 2, the accelerating contactor 15 has only an operating coil 15a which is energized upon operation of a start switch through resistances R, R1, to insert accelerating resistance r in series with the motor 1 and to complete at contacts 15b an energizing circuit for the main switch 2. This switch closes to complete the motor circuit and maintain itself over contacts 2a. It also closes at contacts 2b a reverse circuit for the operating coil of the accelerating contactor 15, including a comparatively high resistance R1, so that the magnetic flux produced by this coil is made to pass through zero whereupon the contactor is released and short-circuits the accelerating resistance r. The invention is described with reference to Figs. 3 and 4, (not shown), as applied to systems operating in a manner similar to those shown in Figs. 1 and 2, but including several steps of accelerating resistances r and a corresponding number of sequentially operated accelerating contactions and resistances R1, the reverse current circuits for each contactor being completed by the operation of the preceding contactor in the sequence.