What are Miniature Circuit Breakers?

Miniature Circuit Breakers (MCB) are used where there is a need for electrical protection. They protect electrical devices such as buttons, relays etc. from overcurrent and short circuits faults. Automatic fuses automatically interrupt current when overcurrent passes through their contacts. There are many components inside MCBs such as switching mechanism, bi-metal opener, electromagnetic opener, main contacts, arc discharge channels and terminals. They are easier and safe to use and operate in electrical panels with smaller sizes than fuses. They offer the convenience of ‘on/off switching’ for circuit isolation since the conductor is housed within a plastic carcass.

How Do MCBs Work?

There are two types of break in fuses.

1- Thermal Protection

When overcurrent flows through the fuse, the bimetallic strip heats up and bends due to expansion. It then separates the contacts by releasing the latch.

2- Magnetic Protection

In case of a short circuit, the current suddenly and excessively rises up. This causes a magnetic reaction. Thus, the contacts of the miniature circuit breaker are separated. This is known as magnetic tripping. An MCB has three principal characteristics, nominal current rating (A), short circuit current rating (kA), and Tripping Curve. Nominal and short circuit current ratings are defined to protect the electrical system which is connected to, if a fault is detected because of overcurrent or short circuit. Nominal current rating is mostly from 0.5 A to 125 A, while short circuit current ratings are generally 6 kA and 10 kA.

The Tripping Curves of Miniature Circuit Breakers

B type: It is used in homes, socket and control circuits.
C type: It is used in inductive loads, protection of loads such as motors, transformers, and many fluorescent lamps.
D type: It is used in the protection of motors with high inrush current, welding, spot machines, sodium vapor lamps, x-ray devices.
K type: It is used for the protection of 24 VDC power supplies.
Z type: It is used in sensitive electronic circuits, limit switch applications, protection of sensor circuits.

VEKMAR supplies all these range of MCBs in stock quantities as official distributor of Schneider Electric, Eaton and LS Electric. We can help you for MCB equipment for your projects with our expert engineering team.