Feedback

Whether the coil of the main contactor is live – what is measured is the phase at the end of the safety circuit, not the position of the contactor contacts. If it does not arrive within four seconds of switching on, or drops out during operation, the device withdraws the command – that is the safety function, not a fault. If the feedback is present although the command is off, the relay on the display board is welded or the coil is fed externally: take the device out of service and notify customer service. A welded contactor itself is not detected by the device. The ladder diagram shows how it fits together, Figure 26.