Improvements in or relating to means for the automatic, quick stopping of electrically-operated machinery

摘要

751,760. Control of A.C. motors. BROOKHIRST SWITCHGEAR Ltd., and DAVIES, A. R. Dec. 23, 1954 [Dec. 24, 1953], No. 35852/53. Class 38(3) A dropper switch DS on a loom closes when a weft thread breaks, for example, so firing a tube E of the three-electrode cold cathode type. This causes operation of a high-speed telephone type relay RS to open the circuit of the alternating- current motor which drives the loom and to close a braking contactor for the introduction of direct-current braking. In a modification, the dropper switch is connected in a circuit the voltage of which is insufficient to fire the tube until the voltage across a capacitor is added to the circuit-voltage by the operation of the switch (Fig. 2, not shown). In another arrangement, the switch DS is in the primary circuit of a step-up transformer the secondary winding of which provides a peak voltage for firing the tube when the switch closes (Fig. 3, not shown).