Patent ID: 7042692
Filing Date: 2006-05-09
Classification: H01F,H01H

Abstract:
1. A drive unit for an electromagnetic device, comprising: a switching control circuit for providing power to a magnetizing coil of the electromagnetic device with an intermittent pulse signal via switching means, wherein said switching control circuit switches the pulse signal so that the switching means which is in an off state is turned on at an initial timing in turn-on timings generated with a predetermined cycle, and the switching means which in an on state becomes the off state at a timing when a detected value of an electric current in the magnetizing coil becomes a predetermined current value, said drive unit closes and releases the electromagnetic device by switching a main switching element of a contact-less relay inserted between the magnetizing coil of the electromagnetic device and an AC power source, and said main switching element in the contact-less relay becomes a non-conductive state for a predetermined time interval longer than the predetermined cycle in a region in a vicinity of zero of a power source voltage below a self-holding current, wherein a predetermined bias signal is superimposed on the detected current value or the predetermined current value at least within a predetermined interval following the time interval of the non-conductive state, and said switching control circuit switches the pulse signal so that the switching means is switched in every predetermined cycle.