in CB high current is flowing n there is small amount of resistance due to friction and its own resistance. so, whichecer amount of resistance is there and the square of high current is higher, consequently the multiplication result s the heat.
First at all, the choice of the CB ( circuit breaker ) should be correctly done accordingly the some points that are :
– The nominal ” In ” current of the CB.
– The correct value of the thermal protection ” Ir “
– The ambiant temperature around the CB, because most of CB are designed accordingly to +30 or +40°C; that means if ambiant temperature around the CB will be more you should absolutly derate the CB accordingly to the ” Derating Temperature ” done by the manufacturs.
– The connection should be done accordingly to the manufacturs instructions specialy for the big currents.
– The connection points should be tighted accordingly to the manufatures instructions.
– The section of cables should be well calculated accordingly to the circulated current.