The Siemens 5SM1616-6BA is a Type A residual-current device (RCD) — an FI protector — in the 5SM6 series, rated 63A at 230V, 2-pole, with a 0.3A (300 mA) rated residual operating current (IΔn). Type A detection means it trips on sinusoidal AC residual currents as well as pulsating DC residual currents up to 6 mA smooth DC — the standard for circuits with single-phase rectifiers, switching power supplies, or variable-speed drives that can superimpose pulsed DC on the line. The 300 mA IΔn is a fire-protection or equipment-protection threshold, not personnel protection (which requires ≤30 mA). It suits sub-distribution boards feeding fixed equipment where the leakage from filters and drives would nuisance-trip a 30 mA device. At 2.5 TE wide (about 45 mm on a DIN rail), it occupies two-and-a-half 18 mm module spaces — a compact footprint for a 63A 2-pole RCD, leaving room in the enclosure for additional protective devices.
The 55 mm depth (D=55 mm) fits standard enclosures without crowding the gland plate. Wired as a main switch or feeder protection RCD in a TN-S or TT system. The 63 A rating covers the full load of a sub-distribution board feeding lighting, socket circuits, and small motor loads — sized for the main incomer, not a single final circuit. For a panel builder: the 2.5 TE width means you can fit this plus a 2-pole MCB in the same 4-module space, keeping the board layout dense. Verify the busbar comb pitch matches the 2.5 TE footprint — standard 4-module busbars may need a half-module adapter.