Behaviour on Loss of Supply
Defines how the system behaves if the supply voltage is interrupted or drops below its limit. The expected behaviour is that the receiver outputs drop out and all motions stop. IEC 62745 addresses behaviour on loss of supply as an explicit heading for wireless control systems.
On a receiver with relay outputs this behaviour comes from the hardware: when the coil is de-energised the contact opens under spring force. However the whole chain must be considered, because loss of supply does not always take the form of a complete interruption.
- Voltage drop: on long control lines the voltage may approach the contactor's drop-out threshold. The contactor chatters, the contacts arc and the risk of welding increases.
- Partial interruption: if the receiver supply is lost while the contactor supply remains, the interlocking logic may be defeated. Feed both circuits from the same source and the same protection.
- Restoration: when power returns, motion must not start of its own accord.
In the AXI product data the supply for the SF100 and ST100 receivers is given as 12/24V DC or 220V AC, and for the SF200 as 12/24V DC; no supply range is stated in the ST200 records. Choose the supply according to this data and fit a separate protective device on the receiver supply.
Context in which this term is used: Wireless Crane Remote Control Selection Guide