What this 4-pole D-curve MCB delivers
The Siemens 5SY8650-8 is a 4-pole miniature circuit breaker from the SENTRON series, with a D tripping characteristic rated at 50 A at 45 °C and a breaking capacity of 20 kA per IEC 60947-2 at 400 V AC. Rated current is temperature-dependent: 50 A at 45 °C, 48.95 A at 50 °C, and 47.85 A at 55 °C.
Breaking capacity and compliance across standards
The 5SY8650-8 carries three distinct breaking capacity ratings depending on the standard applied: 20 kA per IEC 60947-2 at 400 V AC (the industrial standard), 15 kA per IEC 60947-2 at the DC rating, and 5 kA per UL 1077 and CSA C22.2 No. 235. Vibration resistance per IEC 60068-2-6 is ±1 mm at 5 to 25 Hz and 50 m/s² at 25 to 150 Hz, which covers the mechanical stress of a machine-mounted enclosure. Touch protection is integrated on the terminals. The sealable feature allows a lead seal or lock to be applied to the toggle — useful for lockout/tagout procedures where the breaker must be secured in the off position.