The Siemens 5SY7540-8 is a SENTRON miniature circuit breaker (MCB) with a D tripping characteristic, rated 40 A at 230 V AC. The 1P+N pole configuration (2-pole width, 36 mm) switches the phase and provides overcurrent protection on the phase only; the neutral is switched but not protected. Breaking capacity is 15 kA per EN 60898 and 20 kA per IEC 60947-2. The higher 20 kA IEC rating gives additional headroom for industrial panels specified to IEC 60947-2, where the breaker is treated as a circuit-breaker for industrial application rather than a household MCB.
Deployment context
The 36 mm width (2 width units) and 70 mm installation depth fit standard distribution boards and industrial enclosures. Terminal capacity accepts solid or stranded conductors from 0.75 to 35 mm², with combined top and bottom terminals for through-wiring or daisy-chaining. Rated for ambient temperatures from -40 to +70 °C, with derating above 55 °C per the humidity/temperature influence table.