40 A MCCB with TM240 release — line protection duty
The Siemens 3VA1140-5GF46-0AA0 is a 4-pole SENTRON molded case circuit breaker rated for 40 A continuous, with a TM240 thermal-magnetic overcurrent release. The TM designation means it uses a fixed thermal element for overload protection and a magnetic trip for short-circuit events — no interchangeable trip units, so the 40 A rating is locked at order time. At 240 V it interrupts up to 187 kA, which covers most utility-transformer-fed services in North America; at 415 V the breaking capacity drops to 121 kA, still sufficient for most European distribution panels. The 4-pole configuration (three phases plus neutral) makes it suitable for three-phase four-wire systems where the neutral needs overcurrent protection. Rated insulation voltage is 800 V, so it can sit in 690 V line-to-line systems without derating the internal clearances. Power loss at full load is 10.8 W — a useful figure for thermal calculations inside a sealed enclosure. The front face carries IP40 protection, meaning it resists tools and wires larger than 1 mm from entering, but not water ingress; keep it inside a panel, not on a washdown line.
Thermal derating and ambient limits
The 40 A rating holds flat from 40 °C up to 50 °C ambient. Above that it begins to taper: 39 A at 55 °C and 60 °C, 38 A at 65 °C, and 37 A at 70 °C. If the panel ambient runs hot — say next to a drive or transformer — factor in the derating curve rather than oversizing the breaker, because the TM240 release is calibrated to the 40 A thermal element, not a higher frame. Minimum operating temperature is -25 °C; storage range is -40 °C to 80 °C. Physical footprint: 70 mm deep, 101.6 mm wide, 130 mm tall. The width is a standard 4-inch (101.6 mm) module, which fits a typical DIN-rail or panel-mount cutout for a 4-pole MCCB. Depth of 70 mm means it clears most 200 mm deep enclosures with room for wiring gutters.
Breaking capacity across voltages
The interrupting rating drops steeply as voltage rises: 187 kA at 240 V, 121 kA at 415 V, 75.6 kA at 440 V, and 17 kA at both 500 V and 690 V. For a 480 V panel in North America the relevant figure is the 440 V column (75.6 kA) since 480 V is close enough that the 440 V rating governs in practice. At 690 V the 17 kA limit means this breaker is not a high-fault device for 690 V industrial systems — coordinate with upstream fuses or a higher-rated frame if available fault current exceeds that.