What this 40 A MCCB delivers — and what it doesn't
The Siemens SENTRON 3VA2040-6HM32-0AA0 is a 3-pole molded case circuit breaker rated for a continuous current of 40 A across the full ambient temperature range from 40 °C to 70 °C — no derating needed up to that ceiling. That flat thermal curve simplifies panel design: you don't have to oversize the frame for a hot enclosure. The 242 kA breaking capacity at 240 V is the headline number, but the real-world figure for a 400 V distribution board is 187 kA at 415 V and 440 V, dropping to 121 kA at 500 V and 3 kA at 690 V.
Physical fit — panel integration notes
Allow additional clearance for the arc chute exhaust and outgoing cable bending radius.
The rated short-circuit breaking capacity (Icu) is 242 kA at 240 V, 187 kA at 415 V and 440 V, 121 kA at 500 V, and 3 kA at 690 V. For a typical 400 V distribution panel, the 187 kA figure gives substantial headroom for high-fault locations like a main switchboard near a large transformer. The 3 kA at 690 V is low — this breaker is not suited for 690 V industrial grids with significant fault current.