The Siemens 3VA2040-7HM42-0AA0 is a SENTRON molded case circuit breaker (MCCB) rated for 40 A continuous current across its full ambient temperature range from 40 °C to 70 °C — no derating needed up to that ceiling. Its 4-pole design handles three-phase plus neutral, and the 330 kA breaking capacity at 240 V AC means it can safely interrupt fault currents up to that level without upstream cascading, which is the kind of short-circuit rating you spec for high-fault panelboards or transformer secondaries.
Breaking capacity across voltages
This MCCB delivers 242 kA at both 415 V and 440 V, drops to 187 kA at 500 V, and holds 3 kA at 690 V. The steep drop at 690 V is typical for a 40 A frame — the arc extinction limits at higher voltage mean this is a 400 V-class breaker, not a 690 V main. For a 690 V feeder you want a larger frame or a different series.
Mounting and integration
Dimensions are 86 mm deep, 140 mm wide, 181 mm tall — fits standard panel-mount cutouts for a 4-pole MCCB in this frame size. No communication module on board (no Modbus, no PROFIBUS), so it's a straight thermal-magnetic trip unit for line protection, not a smart breaker. Ground-fault monitoring uses summation current formation on L + N, meaning it compares line and neutral current to detect imbalance. No undervoltage release fitted.
Environmental range and power loss
Operates from -25 °C to 70 °C ambient, stores from -40 °C to 80 °C. Maximum power dissipation is 1.2 W — negligible for panel thermal budgeting, but worth noting if you're packing multiple breakers in a sealed enclosure.