The Siemens 5SU1353-0KV40 is a combined residual-current and miniature circuit breaker (RCBO / FI/LS protector) that packs an RCD and an MCB into a single 1+N-pole module. It is listed as Type AC (wave shape) with a rated residual operating current IΔn of 30 mA and a short-circuit breaking capacity of 4.5 kA. The B-curve trip characteristic at 40 A means it handles general-purpose resistive and light inductive loads in a distribution board — the magnetic trip kicks in between 3 and 5 times rated current, so it clears fast on a hard fault without nuisance-tripping on motor inrush.
What the ratings mean for fit
The 30 mA residual sensitivity (IΔn) is the standard for personal protection against direct contact in residential and commercial final circuits per IEC 60364. Type AC detection covers sinusoidal AC fault currents only — if the installation has non-linear loads (VFDs, LED drivers, switched-mode supplies) that generate pulsed DC or high-frequency residuals, a Type A or Type F device is needed instead. The 4.5 kA short-circuit capacity is adequate for domestic and light commercial sub-distribution where the prospective fault current at the board is below that level; for industrial panels with higher fault levels, a device with a higher Icn (e.g., 6 kA or 10 kA) would be specified.