FAQ
【Function】What is a Miniature Circuit Breaker (MCB)?
An MCB is an automatic electrical protection device designed to protect circuits from overload and short-circuit conditions. It disconnects the circuit when a fault is detected and is commonly used in residential, commercial, and industrial power distribution systems.
【Function】What are the main functions of an MCB?
Overload protection : Trips when the current exceeds the rated level for an extended time.
Short-circuit protection : Trips instantly when a sudden, large current surge occurs due to a short circuit.
【Function】How is an MCB different from a fuse?
| Feature | MCB | Fuse |
| Resettable | V， Yes | X，No (must replace) |
| Reusability | High | Single-use only |
| Accuracy | Stable and reliable | Less precise |
| Cost | Higher initial cost, but reusable | Low initial cost |
【Function】What do the C, and D curves on an MCB mean?
These curves represent the trip characteristics, with C/D corresponding to different multiples of the rated current trip.
【Function】How does an MCB work?
An MCB uses two mechanisms:
Thermal trip unit : A bimetallic strip bends due to heat from overload and trips the circuit.
Magnetic trip unit : A magnetic coil activates instantly during a short circuit and trips the breaker.