Gm overcurrent devices are equivalent to which type MCB?

• A. A type
• B. B type
• C. C type
• D. D type

Answer: (C)

Understanding MCB trip curves is key. An overcurrent device carries a magnetic trip that activates at a certain multiple of the rated current, which determines how it responds to inrush and faults. A Gm general‑purpose device is designed to handle typical loads with moderate inrush, so its magnetic trip behavior aligns with the curve used for general-purpose protection. That general-purpose curve trips when the current is around five to ten times the rated current, providing protection while tolerating normal surges. This is why Gm devices are considered equivalent to the C-type MCB. The other curves are chosen for different inrush profiles: some are more sensitive and trip earlier on smaller surges, while others tolerate larger surges before tripping.