The Siemens 5SY7240-6 is a SENTRON miniature circuit breaker (MCB) in a 2-pole configuration, designed for branch-circuit protection in industrial control panels and distribution boards. Its B-curve tripping characteristic (instantaneous trip between 3 and 5 times rated current) makes it a standard choice for resistive and general-purpose loads where inrush is modest — think lighting circuits, control transformers, or small motor starters with separate overload protection. Breaking capacity is rated at 15 kA per EN 60898-1 and 20 kA per IEC 60947-2, with a DC rating of 15 kA at 60 V per IEC 60947-2. At 400 V AC (single- or multi-phase) and up to 440 V, this covers most low-voltage industrial supply points. The UL 1077 supplementary-protector listing at 5 kA means it qualifies as a recognized component for North American panels where a full branch-circuit rated breaker is not required. The 2-pole design switches both phase conductors simultaneously — no neutral switching. This suits single-phase line-to-line loads or two-phase subfeeds. Rated operational voltage is 400 V AC / 60 V DC, with a maximum DC operating voltage of 72 V. Frequency is 50/60 Hz.
Mounting and integration
Occupies 2 modular width units (36 mm) on a DIN rail, with a quick-assembly fastening system and any mounting position. Installation depth is 70 mm; overall depth is 76 mm. The IP20 rating (with connected conductors) is standard for enclosed panel mounting — not for wet or washdown environments. Combined terminals at top and bottom simplify daisy-chaining busbars. Sealable design allows lockout/tagout compliance. Halogen-free and silicon-free construction matters for sensitive environments like semiconductor fabs or clean rooms where outgassing can contaminate processes.
Environmental and derating
Ambient temperature range is -40 °C to 75 °C, with humidity derating: max 95% RH at 55 °C, tapering to 35% RH at 75 °C. Pollution degree 3 (conductive pollution or dry non-conductive that becomes conductive) and overvoltage category III are typical for fixed-installation distribution boards. Energy limitation class 3 indicates good current-limiting performance for downstream equipment protection.