ELECTROMAGNETIC RELAY COMPRISING TWO CONTROL COILS

摘要

The invention provides an electromagnetic relay comprising: a magnetic circuit having at least two free side legs and a middle leg; two control windings arranged respectively one on each of said free side legs; at least two magnetically responsive switch units, each having at least two contact members; each said switch unit being arranged to be activated in response to an electric current in a respective one of the control windings and remain activated owing to residual magnetism in the magnetic circuit after said electric current has ceased; said magnetic circuit further defining a flux path for the magnetic field for each of said control windings such that the magnetic flux from one winding, when a current is passing therethrough, extends through the other winding in a direction to oppose residual flux derived from that other winding, and the flux from one winding, when extending through the other winding is insufficiently strong to activate the switch unit associated therewith, whereby, activation of one switch unit by an electric current in its associated control winding simultaneously causes the de-activation of the other switch unit to provide a bistable action.