26/08/2026
Don’t Just Look at the Amp Rating — Check the Tripping Curve
When selecting a circuit breaker, 40A is only part of the story. The letter also matters.
Take C40 as an example: 40A is the rated current, while C indicates the Type C tripping curve.
Under IEC 60898-1:
🔹 Type B: 3–5×In — for loads with low inrush current
🔹 Type C: 5–10×In — commonly used for lighting, outlets, air conditioners and small motors
🔹 Type D: 10–20×In — suitable for higher inrush loads such as certain motors and transformers
Choosing the right curve helps match breaker behavior to the actual load.