The Siemens 5SU1653-7KV20 is a combined residual-current and overcurrent protective device — an FI/LS protector — in a single 1+N-POL module. It carries a C-curve 20 A overcurrent trip, a 300 mA Type A residual-current sensing circuit, and a 4.5 kA short-circuit breaking capacity. The D=70 mm housing width matches standard Siemens modular devices for DIN-rail panels.
Type A residual-current detection means it catches pulsating DC fault currents from single-phase rectifier loads (switched-mode supplies, LED drivers, variable-speed drives) in addition to sinusoidal AC faults. The 300 mA sensitivity is the standard for fire protection and general shock prevention in fixed installations — not the 30 mA personal-protection threshold, so this unit is sized for sub-distribution or equipment-level protection where the loop impedance and leakage profile allow a higher trip level.