GB765289A - Automatic apparatus for adjusting and testing polar electromagnetic relays - Google Patents

Abstract

765,289. Electromagnetic relays. WESTERN ELECTRIC CO., Inc. March 23,1955 [March 24, 1954, No. 8451/55. Drawings to Specification. Class 38(5) A circuit for automatically adjusting and testing the permanent magnet bias of a polar relay having its fixed contact comprising the permanent magnet so that the relay operates and releases at desired current values, comprises a control circuit responsive to a, switch having two positions, in the first of which the control circuit connects a source of magnetizing current pulses to a coil magnetically coupled to the permanent magnet, the amplitude of these pulses being such as to overmagnetize the magnet, and in the second of which the control circuit connects to the coil a source of variable demagnetizing current pulses of gradually increasing magnitude, the control circuit also selectively connecting to the relay operating coil a source of reset'current of sufficient magnitude to maintain the armature of the relay on the contact being demagnetized during the application of the demagnetizing pulses, or connecting during intervals between the pulses a source of test current the magnitude of which is that required to release the armature from that contact when the relay is correctly adjusted, and a detector responsive to movement of the armature away from the contact to cause the control circuit to terminate the series of demagnetizing pulses. The Specification describes in detail two different circuits for performing the above operations with reference to a relay having two fixed magnetized contacts disposed to either side of the armature. In these circuits a detector is provided for each contact, the control circuit being such that the operation of the first detector to indicate release of the armature from the first contact causes the control circuit to apply demagnetizing pulses to the demagnetizing coil associated with the second contact and operation of the second detector to indicate release of the armature from the sceond contact causes the control circuit to re-apply demagnetizing pulses to the demagnetizing coil of the first contact, demagnetizing pulses being thus applied alternately to the two demagnetizing coils until the detectors indicate immediate release from each contact in turn, whereupon the adjustment is terminated. Specifications 648,656, 691,207 and U.S.A. Specification 2,590,228 are referred to.