| 摘要 |
A device for monitoring the state of relay contacts is especially useful for controlling motor windings in air conditioning systems. When a first relay switch, which is operative to supply power to a first motor winding does not open as desired, a switch monitoring module responsively controls the second relay switch energization to prevent the second relay switch from being closed. This prevents power that would be supplied to a second motor winding from being also supplied to the first motor winding and causing potential damage to the first motor winding. A disclosed example includes an opto isolator that is energized only when the first relay switch is open as desired. The opto isolator controls an output signal to a second relay control portion, which only operates the second relay if the first relay has opened as required.
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