Patent ID: 7368829
Filing Date: 2008-05-06
Classification: G01R,H01H,H02H,Y10T

Abstract:
1. A method for detecting welding in a circuit, the circuit comprising: a DC power supply having a first terminal and a second terminal; a load circuit supplied with electric power from the DC power supply by connecting the load circuit to the first terminal and the second terminal; a first relay having a contact which is inserted between the first terminal and one end of the load circuit; a second relay having a contact which is inserted between the second terminal and another end of the load circuit; and a resistor provided in series with a third relay having a contact, the resistor and the contact of the third relay provided in parallel to the contact of the first relay, the method comprising: shifting from a normal operation state, in which the first relay and the second relay are controlled to be on and the third relay is controlled to be off, to a suspension state, in which the first relay, the second relay and the third relay are controlled to be off, and when shifting from the normal operation state to the suspension state, performing a sequence control to the first relay, the second relay and the third relay while measuring voltage across the one and the other end of the load circuit to individually detect whether the first relay is welded and whether the second relay is welded.