1- MCCB- Molded case circuit Breaker :

MCCB is an electrical protection device that is used for making and breaking power supplies with the protection of overload, earth fault, and short circuits. It is designed for a low voltage distribution system with circuit protection.
It is used in 16 amp to 1600-amp load capacity. It can be operated remotely in auto mode with the help of a shunt coil and the closing coil.

During tripping conditions, a trip alarm circuit is used for alerting faults. It is available in different types of categories such as a current, pole, breaking capacity, and protection type.

2- MCCB Connection Diagram:

3- Working principle of MCCB:

MCCB is an electromechanical protection device on the range of 100A to 1600A, which protests the electrical circuit from over current, short circuit and earth fault. Mainly two function are used MCCB as overload and short circut. Earth fault are also used for additional.

Over Current protection:

Thermal mechanism is used for overload protection. In this mechanism the bimetallic strip are used which is connected into series of load. When main current or load passes through bimetallic strip, if the load is more than capacity then bimetallic strip start to bending and tripping latch held down resultant the circut will be break and equipment will safe.

Short Circuit protection

Electromagnetic mechanism are used for short circuit protection. When short circuit, instantaneous or any major fault is occurred on the circuit then magnetic force is produced on the magnetic coil and megnetic coil push to the tripping latch quickly and circuit is tripped.

4- Parts of MCCB:

MCCB is a combination of electrical and mechanical parts. Varies categories of molded case circuit breaker (MCCBS) are available like frame size, current, pole, breaking capacity, and protection type so many parts are used as per categories. The parts details are given below mentioned.

1- Frame size or molded case

The molded case is used for mounting all components circuit breakers. It is made molded, insulated, and fabricated with the material of glass polyester, thermostat composite resin. It is also known as molded case.
It is made in different categories as per various applications in industries, commercial and residential systems.

2- Operating mechanism:

The operating mechanism is the important part of the circuit breaker which is the main function to open and close contact with the help of a rotating handle. A handle is rotated on and off position. In case of any fault, the breaker tripped and the handle is moved in a central position.

3- Release coil:

• Shunt coil:It is used for remote tripping of protection tripping. It can be operated ac voltage and dc voltage easily.
• Closing Coil: It is used remotely closing from the monitoring room. It is operated on ac voltage and dc voltage.
• Under-voltage: It is used for tripping due to below preset voltage. The value of operating 80% to 110 % and tripping voltage is below 70% of 240 volts or 415 voltages.

4- Arc quenching chamber:

The arc quenching chamber is used for arc quenching during making and breaking contact. It is made of many sheets of the strip for distributing arc.

5- Trip unit or Protection device:

The trip unit is used for the protection of MCCB. It is the important and brain mind of the circuit breaker. Due to any abnormality like a short circuit or over current, the tripping mechanism is operated by the trip unit. Different types of trip units are used.

• Thermal Magnetic release:
• Current sensing electromagnetic device
• Microprocessor-based protection device.

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