| 摘要 |
PROBLEM TO BE SOLVED: To enhance the reliability of monitoring for normally-closed contacts in a relay unit.SOLUTION: A relay unit comprises: a switching circuit 3 that includes one or more normally-opened contacts a1 and a2 and one or more normally-closed contacts b1 and b2, and that becomes in a non-energization state to a load 21 when the normally-opened contacts are in an opening state and the normally-closed contacts are in a closing state, and that becomes in an energization state to the load when the normally-opened contacts are in the closing state and the normally-closed contacts are in the opening state; and a controller 2 that controls the switching circuit. In the non-energization state, the controller transmits a diagnosis signal to the normally-closed contacts and detects a feedback situation of the transmitted diagnosis signal. In a case where the detection result does not satisfy a predetermined condition, the controller re-transmits the diagnosis signal and re-detects the feedback situation of the re-transmitted diagnosis signal. The controller determines it is normal in a case where the re-detection result satisfies the predetermined condition.SELECTED DRAWING: Figure 1 |
