Circuit for rapid excitation and de-excitation of an electromagnetic switch

Claim 1

A circuit for rapid excitation and de-excitation of an electromagnetic switch such as a relay, contactor, magnetic valve, and the like, by direct current, the electromagnetic switch having an excitation winding and an armature controlled in position by the excitation winding, said circuit comprising a choke connected in series with the excitation winding; current supply means coupled to the choke and the excitation winding for providing a flow of steady holding current through the excitation winding via the choke, the current having a magnitude which is adequate for holding a pulled-up armature but inadequate for pulling up the armature from rest position; a first controllable semiconductor switch; a first capacitor connected in a first series circuit arrangement with the first semiconductor switch, the first series circuit arrangement being connected in parallel with the series connected choke and excitation winding and producing a pulse-like current amplification of the holding current in the excitation winding when the first semiconductor switch is controlled; a second controllable semiconductor switch; a second capacitor connected in a second series circuit arrangement with the second semiconductor switch, the second series circuit arrangement being connected in parallel with the excitation winding and producing a pulse-like current reduction of the holding current in the excitation winding when the second semiconductor switch is controlled; a first voltage source for applying a first voltage to the first capacitor for maintaining the first capacitor in charged condition; and a second voltage source for applying a second voltage to the second capacitor for maintaining the second capacitor in charged condition.