The Siemens 3VA2040-6HM42-0AA0 is a SENTRON molded case circuit breaker (MCCB) rated for 40 A continuous current across four poles, with a breaking capacity of 242 kA at 240 V AC. That 242 kA figure at 240 V is the headline interrupting rating — it tells you this breaker can safely clear a fault up to that level without welding contacts or cascading failure upstream. The 800 V rated insulation voltage (Ui) means it's built for 480 V and 600 V class systems as well, though the interrupting curve drops to 187 kA at 415/440 V and 121 kA at 500 V.
Ratings and what they mean for panel fit
The 40 A rating holds across the full ambient range from 40 °C to 70 °C — no derating needed in a warm enclosure. That's a solid advantage for panels packed near motors or drives. The 4-pole construction (switching all three phases plus neutral) is standard for TN-S or TT systems where you need neutral isolation. Ground-fault monitoring uses summation current formation on L + N, so it can detect residual current without a separate GFCI module. Physical footprint: 140 mm wide, 181 mm tall, 86 mm deep. That 86 mm depth is the dimension you'll need clearance for behind the panel door — it's the same depth class as the wider 3VA2 family, so a panel drilled for a 3VA2040-8HN42-0AA0 will accept this unit without rewiring or re-drilling the mounting holes.