What is I2t – Let through Energy ?

I²t – Let through Energy is available thermal energy resulting from Current Flow during circuit opening in Fuse, MCCB, MCB.Unit is A²S (Ampere² Second)

Current limiting circuit breaker has ability break the circuit current lower than the prospective fault current in short-circuit
conditions due breaker operating principle, where fix contact and moving contact in breaker observes current reversal and hence they oppose each other in opposite direction.

For Proper Cable Protection, Let through energy I²t of upstreal SCPD device – Fuse, MCCB or MCB, must be lower than Short Circuit withstand capability of cable. I²t < K²S²