What this MCCB carries and what it means for your panel
The Siemens 3VA1040-3ED32-0DC0 is a 3-pole SENTRON molded case circuit breaker rated for 40 A continuous current (Iu) with a TM210 thermal-magnetic release. That TM210 designation means the thermal fixed at 40 A and the magnetic pickup is adjustable — you set the instantaneous trip threshold to match your load's inrush, not the other way around. Interrupting capacity hits 75.6 kA at 240 V and 52.5 kA at 415 V, so it clears high fault currents without cascading upstream on a 400 V distribution board. The breaker ships with an undervoltage release (UVR) already fitted and two HQ auxiliary switches for remote status. That UVR means the breaker drops out if control voltage falls below the dropout threshold — standard for emergency-stop chains or mains-loss protection on a machine feeder. The 2 HQ aux switches give you one N/O and one N/C contact for the PLC input and the panel lamp, no extra wiring for a third.
Derating and ambient — the numbers that matter for a closed panel
The 3VA1040 holds its full 40 A rating up to 50 °C ambient. Above that it starts to taper: 38.4 A at 55 °C, 37.6 A at 60 °C, 36.8 A at 65 °C, and 36 A at 70 °C. If your panel runs hot — say a VFD cabinet with poor airflow — you need to account for that 4 A drop at the top end. The breaker itself is rated for operation down to -25 °C and stores down to -40 °C, so cold-start in an unheated plant room is fine. Dimensions are 70 mm deep, 76.2 mm wide, 130 mm tall — standard 3-pole MCCB footprint for a 40 A frame. The front face carries an IP40 protection class, meaning tools and fingers stay out, but it's not sealed against washdown. Mount it inside a panel with a gasketed door if the environment is wet.