What It Is and What It Does
The Siemens SENTRON 3VA1140-4EF32-0AE0 is a 3-pole molded case circuit breaker (MCCB) rated 40 A continuous at 40 °C, designed for line protection in industrial power distribution panels. Its TM240 thermal-magnetic overcurrent release provides fixed thermal and magnetic trip elements — no interchangeable trip units, so the breaker is factory-set for 40 A and cannot be re-rated in the field. With an insulation voltage rating of 800 V and a maximum power loss of 10.8 W, this MCCB is sized for standard 3-phase distribution in commercial and light industrial switchboards.
Breaking Capacity — What the Ratings Mean
The interrupting rating defines the maximum fault current the breaker can safely clear at a given voltage. At 240 V AC, this MCCB interrupts 121 kA; at 415 V AC, 75.6 kA; at 440 V AC, 52.5 kA; and at 500 V or 690 V AC, 11.9 kA. These figures govern where the breaker can be applied in the fault-current hierarchy — it will hold coordination downstream of a larger upstream device only if the available fault current stays within these limits. The 121 kA rating at 240 V is typical for high-capacity MCCBs used near large transformers or generator feeds. At 690 V the rating drops to 11.9 kA, so verify the available fault current when applying this breaker on 690 V systems.
Current Rating vs. Ambient Temperature
Rated 40 A from 40 °C to 50 °C, the breaker derates to 39 A at 55–60 °C and 38 A at 65 °C, then 37 A at 70 °C. In a warm enclosure (e.g., above 50 °C), the continuous load must be reduced accordingly to avoid nuisance tripping.
Integration and Mounting
Dimensions are 76.2 mm wide, 130 mm high, and 70 mm deep — a standard 3-pole MCCB footprint for DIN-rail or panel-mount installation in distribution boards. The 70 mm depth is the body-only; allow additional clearance for arc-chamber venting and cable bending radius per Siemens mounting guidelines. This variant ships without undervoltage release, voltage trigger, or ground-fault monitoring, but includes provision for up to 4 auxiliary switches (HQ type) for remote status indication.