Siemens SENTRON 5SY7240-7 — 2-pole C-curve MCB for panel builders
The Siemens 5SY7240-7 is a 2-pole miniature circuit breaker from the SENTRON family, designed for branch-circuit protection in industrial control panels. Its C-curve tripping characteristic suits moderate inrush loads — motor starters, contactor coils, and small transformers — where the magnetic trip threshold sits between 5 and 10 times rated current, avoiding nuisance trips on startup while still clearing short circuits fast. Breaking capacity is certified under three standards: 15 kA per EN 60898-1, 20 kA per IEC 60947-2, and 15 kA at DC per IEC 60947-2. That 20 kA rating at 400 V AC means it can interrupt fault currents up to that level without welding contacts or cascading failure upstream — important for selectivity coordination in a multi-breaker panel. The DC rating at 60 V covers control-circuit protection where a 60 V DC supply feeds relay coils or solenoids. Dimensions: 36 mm wide (2 modular width units), 90 mm high, 76 mm deep. Installation depth is 70 mm. Snap-on mounting to DIN rail, any mounting position. IP20 with conductors connected.
Certification and compliance documentation
Certified to IEC / EN 60898-1 and IEC / EN 60947-2, plus UL 1077 — the UL 1077 listing covers supplementary protectors for North American panels, while the IEC 60947-2 rating qualifies it for industrial circuit-breaker duty. Halogen-free and silicon-free construction supports use in clean-room or electronics-manufacturing environments where outgassing contaminants must be minimised. Pollution degree 3 and overvoltage category III suit fixed installations inside industrial enclosures. Sealable — the toggle can be locked in the off position for lockout/tagout compliance.
Environmental range and terminal details
Ambient temperature range spans -40 °C to +75 °C (–), with derated humidity limits: 95% RH up to 55 °C, 55% RH up to 70 °C, 35% RH up to 75 °C. Combined terminals top and bottom (–) accept busbar or cable entry from either direction. Neutral conductor is not switched — this is a 2-pole breaker with both poles protecting line conductors, not a 1P+N configuration.