ABB ST203M-K4 Soft Starter 3-Phase Motor Controller

ABB ST203M-K4 is a three-pole miniature circuit breaker (MCB) in ABB’s ST-compatible line, engineered to protect 3-phase circuits in low-voltage installations with a rated current of 4 A. Configured for a 480Y/277V AC supply, it delivers up to 10 kA short-circuit interrupting capacity and uses a K-curve tripping characteristic suitable for circuits with moderate inrush, making it appropriate for protecting motor feeds and other automated loads in control panels. Listed to UL 1077 as a supplementary protector, the ST203M-K4 provides reliable overload and short-circuit protection in a compact package that fits standard industrial distribution boards. Typical applications include safeguarding motor control panels, machine mains, and other 3-phase equipment where precise current protection and fast disconnection are required, aligning with ABB’s engineering standards for safe, responsive electrical protection.