For a small three‑phase motor — a 3 kW compressor, a conveyor drive, or a workshop lathe — the ABB S203‑K16 provides motor‑friendly overcurrent protection in a compact 52.5 mm package. The K curve’s 8×In magnetic threshold (128 A) lets the motor start without tripping, while the thermal overload protects against sustained overcurrent and eventual burnout.

Why a 3‑Pole K Curve
Three‑phase motors are common in light industrial and commercial settings. The S203‑K16 switches all three phases simultaneously, disconnecting the motor completely. This is critical for safety during maintenance and for compliance with isolation requirements. The K characteristic is specified in DIN VDE 0660 for motor control circuits, making it the correct choice for this application.

Electrical and Mechanical Specifications
The S203‑K16 is rated for 230/400 V AC and 72 V DC, with a breaking capacity of 6 kA (Icn per IEC/EN 60898-1). Some sources, including RS Components, note a higher Icu of 20 kA at 400 V under IEC/EN 60947-2; the lower 6 kA remains the conservative rating for general household‑type installations. The device occupies 52.5 mm width (3 modules) on a 35 mm DIN rail. Terminals accept solid conductors up to 25 mm² or stranded up to 16 mm², torque 2.8 N·m. Operating temperature –25 °C to +55 °C. Mechanical and electrical endurance are both 20,000 cycles.

Motor Sizing
The 16 A rating typically suits three‑phase motors with a full‑load current of 12–14 A, which corresponds to approximately 3–4 kW depending on efficiency and power factor. Always consult the motor nameplate. For a motor with a FLC of 14 A, the S203‑K16 provides adequate headroom for starting currents while still offering effective overload protection. For higher power motors, move up to a 20 A or 25 A K curve breaker.

Installation and Coordination
Mounts on 35 mm DIN rail per EN 60715. The device can be fed from top or bottom. For motor circuits, the breaker should be combined with a contactor if the motor is started frequently, as manual switching of the breaker is not intended for high‑cycle duty. Auxiliary contacts (S2C‑S/H6R) can be added for remote status indication. The S203‑K16 also accepts shunt trips and undervoltage releases.

Compliance and Origin
Manufactured in Germany. Complies with IEC/EN 60898-1 and IEC/EN 60947-2. UL 1077 recognized. RoHS compliant, SVHC‑free. EAN: 4016779496155.