The Siemens 5SU1353-6KV40 is an FI/LS-protector Type A (PSE/SSF) combining residual current and overcurrent protection in a single 1+N-pole unit. Rated at B-curve 40A with 30mA sensitivity and 4.5kA breaking capacity, it covers final circuits needing both earth-leakage and short-circuit protection in a compact 70mm-wide package.
What the ratings mean for fit
The Type A classification means it detects pulsating DC residual currents as well as sinusoidal AC — essential for circuits with single-phase rectifiers, switching power supplies, or variable-speed drives that generate smooth DC fault currents. Standard Type AC devices would not trip on those waveforms. The B-curve 40A overcurrent element trips instantaneously at 5 to 10 times rated current (200–400A), sized for resistive and moderate inductive loads like lighting banks, small motor circuits, or socket outlets. The 30mA residual threshold meets the 30mA limit for personal protection against direct contact per IEC 60364. Rated breaking capacity of 4.5kA at the declared voltage suits residential and light commercial distribution boards where prospective fault current stays below that level. For industrial panels with higher SCCR, verify coordination with the upstream device.