It protects branch circuits against overload and short-circuit in industrial control panels, distribution boards, and mechanical-engineering installations. Breaking capacity is 6 kA per EN 60898-1 and 10 kA per IEC 60947-2 / UL1077. The higher 10 kA figure applies when the breaker is specified under the industrial standard, which is the relevant one for most panel builders coordinating with upstream devices.
Ratings and thermal derating
The 40 A rating holds at 35 °C ambient. Above that, derate linearly: 37.56 A at 40 °C, 36.28 A at 45 °C, 34.96 A at 50 °C, and 33.6 A at 55 °C. If the panel internal temperature runs at 50 °C, the effective continuous current is just under 35 A — plan the load accordingly. Energy limitation class 3 indicates the breaker limits let-through energy to a level that protects downstream components during a short-circuit, which simplifies coordination in a distribution board.
Combined terminal top and bottom accept supply from either side. Neutral conductor is not switched — this is a 2-pole breaker switching both phases (line and load) in a single-phase or split-phase circuit, not a 1P+N device.