GB261507A - Improvements in or relating to control systems for electrical apparatus, such as motors - Google Patents

Abstract

261,507. Scarf, C. T., and Metropolitan- Vickers Electrical Co., Ltd. Sept. 21, 1925. Cut-out arrangements. - In a protective control system for coal-cutting machinery, the manual operation of the reversing control switch 24, 25, 26 located near the motor causes the subsequent operation of a pilot switch 28 connected therewith, the pilot switch serving to complete a low-voltage circuit (deriving its energy from a transformer 43, 46 across a pair of the phases) to energize, through the earthed armouring 42, 41 and a pilot wire 48, 49 of the five-core trailing cable, the closing coil 47 of a closing relay 52 for the remotely disposed main circuit-breaker. The closure of the relay 52 completes the circuit across the phases 2, 3 of the closing coil 50 of the main circuit-breaker. In this circuit the contacts 51 of a normally closed no-volt relay are arranged, its operating coil 54 being connected across the phases 2, 3 through the contacts 55 of a leakage relay and the contacts 56 of an overload relay. The leakage relay is energized by the secondary coil 6 on the core 5 when a leakage occurs in any one of the phases a turn of each of which is taken round the core, as shown. The overload relay has a core energized by turns 121, 122 of two of the phases. In the event of leakage or overload, the no-volt relay assumes the off-position and, in consequence, the closing coil 50 of the main circuitbreaker is de-energized. The no-volt relay can be reset by closing the push-button switch 53. In stopping the motor in normal working the operating handle 60 first opens the pilot switch thereby causing the opening of the main circuitbreaker. In order further to ensure that the power circuit is never broken at the control switch, an electromagnetic latch device is employed consisting of a core 27 energized from one of the phases and serving to engage a sector 62 on the spindle of the operating lever 60 and thereby lock the lever while current is flowing.