Patent ID: 6768615
Filing Date: 2004-07-27
Classification: H01H

Abstract:
A relay control circuit for connecting a power source supplying an alternating current having a power voltage and a load, the relay control circuit comprising:a relay provided with a coil and at least one contact, the contact being operable between a closed operational position where the alternating current is allowed to pass to the load and an open operational position where the supply of the alternating current to the load is cut off, the contact being actuated responsive to energization of the coil, the relay having in operation at least one characteristic time lag; a control unit operable to energize the coil of the relay responsive to a received turn-on or turn-off switch signal; a time delay parameter storage means connected to the control unit and storing a time delay parameter, the time delay parameter corresponding in value to the time lag; and, a first voltage detection device for detecting a voltage zero-crossing point of the power voltage and generating a first voltage zero-crossing signal to the control unit; wherein the control unit is operable to control energization of the coil based upon the time delay parameter to actuate a transition between the operational positions of the contact in substantially time-aligned manner relative to the first voltage zero-crossing signal, whereby the contact is actually operated at a time that the power voltage is substantially zero in value; and, wherein the control unit is operable to update the time delay parameter in value based upon a measurement of the power voltage at a load-side point relative to the contact.