What this 40 A 4-pole C-curve MCB is
The Siemens 5SY4440-7CV is a 4-pole miniature circuit breaker (MCB) from the SENTRON 5SY4 series, rated 40 A with a C tripping characteristic and a 15 kA breaking capacity certified to IEC / EN 60947-2.
The 15 kA breaking capacity at 400/440 V AC meets the fault level expected in most industrial distribution boards downstream of a larger upstream breaker. Temperature derating is published: at 35 °C ambient the 40 A rating holds; at 50 °C it's 35.4 A, and at 55 °C it's 34.2 A. Plan your continuous load at the panel's worst-case ambient, not the 40 A nameplate. The IP20 rating applies only with connected conductors — the terminals are finger-safe once wired.
Deployment context
At 72 mm wide (4 MW), it consumes one standard slot in a 12- or 24-way distribution board. Rated for use in mechanical engineering and general industry environments per the suitability listing.