What it is and what it does
The Siemens 5SY4540-5 is a 2-pole (1P+N) miniature circuit breaker from the SENTRON 5SY4 family, rated 40 A with a Type A tripping characteristic. Type A trips on short-circuit and overload, with a defined sensitivity to pulsating DC fault currents — useful where downstream electronics or rectified loads could produce half-wave faults that a Type B or C might miss. The 10 kA breaking capacity per EN 60898 covers standard residential and light commercial panel fault levels; the 15 kA rating per IEC 60947-2 gives headroom for industrial distribution boards where the prospective short-circuit current is higher. Rated 230 V AC with a maximum DC voltage of 72 V, it handles single-phase AC branch circuits and low-voltage DC loads like control transformers or solenoids. The 5 kA interrupting rating per UL 1077 / CSA C22.2 No. 235 means it is recognised as a supplementary protector for North American panels — not a branch-circuit rated breaker under UL 489, so verify the application's code requirements if you are specifying for a UL-listed panel.
Mounting and integration
Snaps onto DIN rail via the quick-assembly system (mounting position any, so horizontal or vertical orientation is fine). Occupies 2 width units (36 mm) with a depth of 76 mm and an installation depth of 70 mm — standard 36 mm wide MCB footprint, no surprises for panel layout. The combined top and bottom terminals accept solid or stranded conductors from 0.75 to 35 mm², which covers most branch-circuit wiring sizes up to a 40 A load. IP20 with connected conductors — protected against finger contact but not against moisture, so install inside an enclosure rated for the environment. Sealable (yes) for applications requiring tamper-evident covers. Halogen-free and silicon-free construction suits clean-room or sensitive electronics areas where outgassing could contaminate contacts or optics.
Environmental and lifecycle
Approvals include EN 60898 (household-type MCB), IEC 60947-2 (industrial circuit-breaker), and UL 1077 / CSA C22.2 No. 235 (supplementary protector). Overvoltage category III means it is rated for fixed installation downstream of the main distribution board. The product designation (miniature circuit breaker) and design (5SY4) align with the SENTRON portfolio for panel-building and industrial switchgear.