What it is and what it does
The Siemens 3VA1050-3ED42-0DH0 is a SENTRON molded case circuit breaker (MCCB) — a 4-pole, 50 A rated device with a TM210 thermal-magnetic trip unit, built for line protection in distribution panels and motor control centers. Rated continuous current Iu is 50 A, and it carries a rated insulation voltage Ui of 800 V, so it's sized for 690 VAC systems with headroom on the insulation side. Breaking capacity runs from 75.6 kA at 240 V down to 7.5 kA at 690 V — that 75.6 kA figure at 240 V means it can interrupt very high fault currents on low-voltage distribution, typical for transformer secondaries or large bus risers. The TM210 thermal-magnetic trip handles overloads (thermal bimetal) and short-circuits (magnetic coil) in one package — no separate electronic trip unit to program or power.
Thermal derating — the real-world current
This breaker holds its full 50 A rating from 40 °C through 50 °C ambient. At 55 °C it derates to 48 A, at 60 °C to 47 A, and at 70 °C to 45 A. That curve matters if you're packing it into a hot panel or near other heat sources — the 50 A number is only valid up to 50 °C.
Auxiliary and undervoltage release
Factory-fitted with 2 auxiliary switches plus 1 trip alarm switch (HQ configuration) and an undervoltage release (UVR). The UVR trips the breaker when control voltage drops — standard for emergency-stop chains or undervoltage protection schemes. The auxiliary contact version is 2 auxiliary switches + 1 trip alarm switch HQ. The integrated auxiliary trip is order code 3VA9608-0BB25 — if you're replacing just the aux block, that's the spare part number.
Mounting and environment
Dimensions: 130 mm high, 101.6 mm wide, 70 mm deep. That 101.6 mm width is exactly 4 module spaces on a standard DIN rail — it clips onto the rail and locks in place. Front protection is IP40, so it's splash-resistant from the front but not sealed for washdown. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. The storage limit governs handling and warehousing, not running.