Direct current interruption on small AC relay using IGBT commutation circuit with surge protection element

Relay is a switch to break or to connect an electric circuit by an electromagnetic force. When a direct current is interrupted, an arc occurs between the relay contacts. And the relay may be destroyed by the damage of burning and/or melting. One method of the direct current interruption is commutation. A bypass circuit (commutation circuit) is constituted by connecting a commutation element to the relay contacts in parallel. The arc would not occur by diverting the circuit current to the commutation circuit when the contacts are interrupted. And then, the circuit current would decrease with the increasing of the resistance value of the commutation element by time. Finally, when another relay is opened, the circuit completely turns off without arcs. In this study, two cheap AC relays (the rating: 125V – 10A) and an IGBT as a commutation element are used. In addition, surge protection properties are measured when the circuit has an inductive load. As a result, the circuit current of DC 100V – 10A was interrupted with controlling surge voltage successfully.