The Siemens 5SM1346-6FD is an FI-Protector Type A RCD rated 63A, 4-pole, with a 30mA trip sensitivity at 400V. Type A detection handles pulsating DC fault currents on top of AC sine-wave leakage. The 55mm depth is standard for this class of RCD, so it clears typical enclosure depths without interference.
63A continuous rating means this RCD handles the full load of a submain feeding a mixed load of lighting, general-purpose sockets, and small motor circuits — not a single motor branch. The 30mA sensitivity is the touch-protection threshold: it'll trip on leakage above 30mA, which is below the let-go current that can cause ventricular fibrillation. For a food-processing line or a pharmaceutical clean room where washdown introduces moisture, that sensitivity catches incipient ground faults before they become arc faults. Type A is the right choice when the downstream loads include single-phase rectifiers. A plain AC-type RCD can blind itself to pulsating DC leakage and fail to trip. Type A sees those half-wave pulses and clears them. If your installation has three-phase VFDs with DC-link smoothing, you'd step up to Type B (all-current sensitive), but for most mixed-use distribution boards this Type A covers the common case.