What it is and what the ratings mean
The Siemens 5SM3647-4BG is a 4-pole residual current operated circuit breaker (RCCB) in Type B, rated at 80 A continuous current with 300 mA sensitivity on a 400 V AC system, and it carries a short-time delay characteristic. Type B detection covers AC sinusoidal, pulsating DC, and smooth DC fault currents up to 1 kHz — the full spectrum you'd see from variable-frequency drives, UPS systems, or PV inverters. The 300 mA threshold is the standard for fire protection in commercial and industrial panels, not personnel shock protection (that's 30 mA). The short-time delay means it rides through nuisance trips from inrush or transient earth faults, coordinating downstream with instantaneous RCCBs.
Lifecycle and sourcing reality
For a BOM line that calls out this exact order code, fit is confirmed by the ratings above: 80 A frame, 4-pole, Type B, 300 mA, 400 V AC, short-time delayed. Sourced and quoted to order against an RFQ through independent distribution; availability and current pricing confirmed at quote time.
Where it goes in the panel
Snap-on DIN rail mount, standard 4-module width. The 80 A rating means it feeds a sub-distribution board or a heavy load group — think multiple drives or a large UPS output circuit. The Type B characteristic makes it mandatory downstream of any VFD or inverter that can generate DC fault current; a standard Type A RCCB would blind-trip or fail to detect a smooth DC fault.