What this MCCB carries — and where the ratings matter
The Siemens 3VM1140-3GE42-0AA0 is a 4-pole SENTRON molded case circuit breaker rated 40 A continuous, with a TM220 thermal-magnetic release for line protection. The interrupting capacity is 76 kA at 240 V AC, 53 kA at 415 V AC, 32 kA at 440 V AC, and 12 kA at 500 V AC — so at 415 V it handles a 53 kA fault without upstream cascading, which is the number most panel builders check first for industrial distribution. Rated insulation voltage is 800 V, and the maximum operating voltage is 690 V AC or 500 V DC. The 4-pole construction means it switches all three phases plus neutral, common for three-phase four-wire systems where you need full isolation on the neutral leg.
Thermal derating — what the current curve actually means
The 40 A rating holds flat from 40 °C through 50 °C ambient. At 55 °C it derates to 39 A, at 65 °C to 38 A, and at 70 °C to 37 A. If your panel internal ambient runs above 50 °C — say a tightly packed enclosure near a furnace line — you lose 3 A by 70 °C. That's a 7.5 % reduction, enough to matter on a fully loaded circuit.
Physical fit and panel integration
The breaker measures 101.6 mm wide, 130 mm tall, and 70 mm deep. Front IP40 protection is standard for indoor panel mounting. Maximum power loss is 11 W — negligible for thermal budgeting in a ventilated panel, but worth noting if you're packing multiple breakers in a sealed enclosure.