What do MCB types B, C and D mean?

see full answer

Your Exam Success, Personally Taken Care Of

1:1 expert mentors customize learning to your strength and weaknesses – so you score higher in school , IIT JEE and NEET entrance exams.

An Intiative by Sri Chaitanya

(Unlock A.I Detailed Solution for FREE)

Best Courses for You

JEE

NEET

Foundation JEE

Foundation NEET

CBSE

Detailed Solution

The "Type" of an MCB (B, C, or D) refers to its tripping curve, specifically its magnetic trip sensitivity. It defines how much of a current surge (multiple of its rated current) is required to make the MCB trip almost instantly.

Type B: This is the most sensitive type. It is designed to trip at 3 to 5 times its rated current (In).
- Use: Primarily for domestic and residential applications with mainly resistive loads like lighting circuits, outlets, and appliances without large motors. It provides excellent protection for people and cables without nuisance tripping.
Type C: This is the most common, general-purpose type. It is designed to trip at 5 to 10 times its rated current (In).
- Use: For commercial and light industrial applications with mixed and inductive loads, such as fluorescent lighting, small motors (fans, pumps), and everyday appliances. It offers a good balance, tolerating small motor start-up surges while still providing solid protection.
Type D: This is the least sensitive type. It is designed to trip at 10 to 20 times its rated current (In).
- Use: For heavy industrial applications with equipment that has very high inrush currents, like large motors, transformers, and welding machines. This type prevents the MCB from tripping every time such heavy machinery is switched on.