Improvements in or relating to protective switches for electric motors

摘要

246,511. Siemens - Schuckertwerke Ges. Jan. 24, 1925, [Convention date]. Automatic curcuit-breakers; cut-out systems.- An automatic switch for protecting a motor against no-volt and overload conditions is delayed in action by a hot wire 31 normally holding in position a latch 28 which prevents release of the no-volt magnet armature 26 during short fluctuations of potential in the line. In the three-phase apparatus shown the wire 31 is heated by current induced in a coil 34 associated with the no-volt magnet coil 25. The movable switch contacts 3 are closed through collapsable toggle links 10, 11, 12 by a handle 5, which also closes an auxiliary switch 38 to connect the no-volt magnet across two phases of the supply. Tripping members 20 are made to strike the toggles either by movement of the no-volt armature 18, or by movement of overload plungers 18, but unless the overload is considerable a spring blade 47 making contact with two stop terminals 39, 40 arrests the action, which is completed by the novolt armature after the short-circuiting of the coil 25 and is subject to the delay due to the hot wire.