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. 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.
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. 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.
Approvals include EN 60898 (household-type MCB), IEC 60947-2 (industrial circuit-breaker), and UL 1077 / CSA C22.2 No. 235 (supplementary protector). The product designation (miniature circuit breaker) and design (5SY4) align with the SENTRON portfolio for panel-building and industrial switchgear.