Selecting Fuses for Switch Gear Relay


Thread Starter


We have a interposing relay panel with relays inside for switch gear MCC start stop and trip. Vendor is requesting us to provide the fuse rating for the DO signals terminals?

please share some information with formulas for how to calculate for selecting fuse at terminals

if possible please email me on [email protected]
It's not a "formula". You simply read what the current rating of the contacts are on the relay you are using, and the current rating of anything that those circuits are connected to, and use the lowest of any value.

For example you are using a relay with contacts rated for 10A, but the circuit is feeding a PLC input that is rated for 2A maximum, you fuse the circuit at 2A. If the relay has contacts rated at 5A max and the maximum current on the PLC input it 6A, you fuse it at 5A.
if you want a formula, usually a fuse is selected as 1.7 times the nominal current of a circuit.