Abb Oy

Abb Inc.

Ilkka T Pajari

Kalyan P Gokhale

Matti T Jussila

Douglas W Karraker

A system for the detection of welded contacts in a circuit of a line converter system has a plurality of inverter switches, a plurality of utility switches in which a pair of utility switches is connected in series through a line to a utility, a voltage detector, an electronic controller, and a DC input source. The line converter system converts incoming DC power into AC output power that is delivered to the utility grid. The voltage detector measures the voltage across a first node and a second node of the circuit and provides an output that is interpreted by an electronic controller for each step performed during a method of detection of welded contacts. The detection method has a sequence of test steps in which at least one switch is opened and/or closed, a DC bus of the inverter or the utility grid is used as a stimulus voltage, and the voltage is measured. If a voltage is not detected across the first and second nodes, the test sequence is continued until a welded contact is detected or the electronic controller determines that none of the contacts are welded. If the controller determines that none of the contacts are welded, the line converter system is permitted to connect and supply AC power to the utility.

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Milwaukee, WI, United States of America

Ilkka T Pajari