What the ratings mean for fit
The Siemens 3VA1120-5EF36-0KH0 is a SENTRON molded case circuit breaker (MCCB) for line protection, rated 20 A continuously at 40 °C ambient — no derating needed up to 55 °C, then it steps down to 19 A at 60–70 °C. That thermal curve means you can load it at 20 A in most panel environments without oversizing the frame. The 121 kA breaking capacity at 415 V is the figure that governs fault clearing on a 400 V distribution bus; it safely interrupts a bolted fault up to that level without cascading upstream. Three poles, 70 mm deep, 76.2 mm wide, 130 mm tall — fits standard MCCB panel cutouts and DIN-rail adapters. Insulation voltage is rated 800 V, so the breaker is suited for 480 V and 600 V class systems as well — the 121 kA at 415 V is the highest published interrupting rating, but the 17 kA at 690 V confirms it can handle 690 V line-to-line with lower available fault current. The shunt trip (STL) allows remote tripping from a safety relay or emergency-stop circuit; the auxiliary switch configuration (2 aux + 1 trip alarm) gives status feedback for PLC or SCADA.
Sourcing and lifecycle
Maximum power loss is 12 W at rated load — negligible for panel heat budgeting but worth noting if the breaker is enclosed in a small, sealed sub-panel.
Deployment context
Mounts in a standard MCCB footprint on DIN rail or panel-mount base. The 3-pole design is typical for three-phase motor branch circuits, distribution feeders, or transformer protection. The shunt trip and auxiliary switches are factory-fitted, so no field assembly of internal accessories is required — wire the control voltage to the STL coil and the aux contacts back to the PLC input card.