5SY4450-7CV MCB, 15kA 400V 4P C50, current production

The Siemens 5SY4450-7CV is a 4-pole miniature circuit breaker (MCB) with a C50 trip characteristic and a short-circuit breaking capacity Icu of 15 kA at 400 V. The C50 curve means it trips between 5 and 10 times rated current (50 A), so it's sized for motor or transformer inrush without nuisance tripping on moderate overloads. The 15 kA Icu at 400 V tells you it can safely interrupt fault currents up to that level on a 400 V three-phase supply — a standard requirement for industrial panel feeders where the prospective short-circuit current is high. This is a DIN-rail mounted device, so it clips directly into the panel's distribution board alongside other modular protection gear.