What it is and what it does
The Siemens SENTRON 3VA1150-3EF36-0JH0 is a 3-pole molded case circuit breaker (MCCB) rated for 50 A continuous current at 40 °C, with a TM240 thermal-magnetic overcurrent release and an integrated shunt trip (STL) auxiliary release. It's built for line protection — meaning it sits on the feeder or main branch of a distribution panel, not on a motor or specific load. The interrupting ratings tell you where it can clear a fault: 75.6 kA at 240 V, 52.5 kA at 415 V, 32 kA at 440 V, and 10.5 kA at 690 V. That 75.6 kA figure at 240 V is what you'd check first if this breaker feeds a low-voltage transformer or a high-fault panel — it's the highest short-circuit current it can safely interrupt without welding contacts or venting plasma.
Thermal derating and real-world current
The 50 A rating holds flat from 40 °C up to 50 °C — that's the sweet spot for most enclosed panels. Above that, it starts to taper: 48 A at 55 °C, 47 A at 60 °C, 46 A at 65 °C, and 45 A at 70 °C. If your panel runs hot near the top of that range, you lose 5 A of headroom; plan the load accordingly rather than pushing the breaker to its nameplate. Rated insulation voltage is 800 V, so it's comfortable on 480/277 V and 600 V systems with margin. The storage range of -40 °C to 80 °C means it can sit in an unheated warehouse or a hot trailer without damage — just don't energize it outside the -25 °C to 70 °C operating window.
Physical fit and auxiliaries
The breaker measures 76.2 mm wide, 130 mm tall, and 70 mm deep — a standard 3-pole MCCB footprint for a 50 A frame. It carries 2 auxiliary switches plus 1 trip alarm switch (HQ type), which gives you status feedback for the PLC or SCADA without needing an external relay pack. Front protection is IP40 — fine for a clean indoor panel, but not for washdown or outdoor exposure. The shunt trip (STL) allows remote tripping via a control signal, useful for emergency-stop circuits or remote disconnect schemes. There's no undervoltage release, no phase-failure detection, and no communication module — this is a basic thermal-magnetic breaker, not a smart metering device.
Lifecycle and sourcing reality
The integrated auxiliary trip uses a separate order code (3VA9688-0BL32) — if you're replacing a failed unit, make sure that shunt trip module comes with the new breaker or is ordered alongside it.