What is MCCB ?

 A moulded case circuit breaker (MCCB) is a type of electrical protection device that is used to protect the electrical circuit from excessive current, which can cause overload or short circuit.

MCCB is the device that is manufactured as an integral inner supporting an enclosed housing of insulating material. It is required for making, carrying, and breaking currents between separate contacts under normal circuit conditions and abnormal circuit conditions such as those of overload condition and short circuit conditions. MCCBs provide protection to the low-voltage distribution systems.

Quenching the arc in the air inside the moulded case, the MCCBs interrupt current with a range from few amperes to several kilo-amperes. MCCBs are useful for protecting the system against faults like Overload & Short Circuit, with the help of release which may be Thermal Magnetic or Microprocessor Type. MCCB satisfies the requirement of isolation as it provides complete isolation to the circuit. Compact Size, Lower Downtime, Reduction in inventory & Availability of various accessories makes it a distinctive product.

Specifications of MCCBs:

Ue – Rated Operational Voltage

Ui – Rated Insulation Voltage

Uimp – Impulse withstand voltage

In – Nominal Rated Current

Ics – Service Short Circuit Breaking Capacity

Icu – Ultimate Short Circuit Breaking Capacity

Components of Molded Case Circuit Breakers

Operating Mechanism: The Operating Mechanism handles the opening and shutting of the contacts. The speed that the contacts open or close is free of how quick the handle is moved. The breaker can’t be kept from stumbling by holding the handle in the on position. The handling will be in a halfway position when the contacts are stumbled.

Arc Extinguisher: An arc is made at whatever point an electrical switch interferes with a present stream. The Arc Extinguisher’s activity is to limit and separate that circular segment, subsequently stifling it. At the point when an intrusion happens and the contacts partitioned, the present course through the ionized area of the contacts actuates an attractive field around the bend and the circular segment douser.

Trip Unit: The Trip Unit is the cerebrum of the electrical switch. The capacity of the unit is to trip the working system in case of an abnormal condition. Electronic trip units are presently accessible and they can give considerably more refined insurance and observe.

The MCCB Working in itself is an incredible invention. The MCCB is a choice to wire since it needn’t bother with a substitute once an over-burden is taken note. Dissimilar to wire, this electrical switch can be just reset after a misstep and offers improved administrator security and straightforwardness without procuring working expense. For the most part, these circuits have a warm current for overcurrent and the attractive component for impeding to work quicker.

 There are several advantages of the MCCB:  

MCCBs are Compact in the measure. Hence it spares a significant space inboard plan.

MCCBs have to limit downtime. Dissimilar to in a breaker-based framework, there’s no looking for a substitution intertwine. It very well may be Reset and Switched-On again instantly in the wake of finding the blame that caused the stumbling amid activity.

MCCBs can clear a few blame previously it is expected for substitution.

MCCBs are “Upkeep Free” and its repeating costs are less.

At the point when MCCBs are utilized, at that point, there is no probability of single staging because of blame in just a single stage.

Some multi-reason adornments can be fitted with the MCCB.

MCCB with the combination of one of the two different trip elements will protect the circuit against situations such as: 

Thermal Overload:

In the conditions of overload, there is a temperature between the insulation and conductor. If the insulation remains unchecked, its life will reduce and the maintenance would be higher. It is important to catch the approach of MCCB for the better flow of circuit and lifelong approach of the product.

Short-circuit Condition:

It is the condition due to an intentional or unintentional low impedance path creation between phase wires or a neutral & phase wires, this situation leads to an excessively high current flowing through the circuit & voltage becomes negligible

Ground Fault condition:

It is also the type of short circuit which is linked with the ground phase. This is the common fault which takes place in the low voltage.

The MCCB protects the huge amount of mess and protects the system while enhancing the capability. The MCCB is highly durable and the life of these gadgets is longer than usual gadgets. It is suitable for the higher energy impact. The gadget must be installed by the professional because it is not that easy to be installed and once it is done, you are free to form the obstacles that you might face regarding electricity, short-circuits, and the low-voltage.

Nowadays MCCBs are available with 2 kinds of release, one is with thermal-magnetic &other is microprocessor release.

Thermal-magnetic uses the principle of the bimetal and electromagnetic coil. Thermal protection is required for O/L & electromagnetic or solenoid is used for S/C. but since electromagnet is a peak sensing device thus a slight transient peak can cause nuisance tripping of MCCB. This CB gives the following protections

Thermal /Overload Protection- Through Bimetal

Electromagnetic /Short Circuit Protection- Through Electromagnet

Under Voltage Protection- Through U/V Release

Microprocessor or electronic release sense true R.M.S value of current. It is simulated and calculated from peak values, which are detectable by a microprocessor. The microprocessor-based release may offer below protections which can be add on:

Earth Fault

Neutral protection

Instantaneous Over-ride

Earth Leakage

Current Unbalance

Overvoltage

Wrong Selection of MCCB:

For a few special applications, manufacturers recommend using MCCBs dedicated to that application. For Ex. For motor back up protection, there is a requirement for overload protection of the motor, it is required to match the overload settings of MCCB with that of the motor. This solution assures no damage to the motor in case of motor overloading. However, the life expectancy of contactor as per the circuit design is considered better than that of MCCB. Hence this combination will give a much lesser life, thus it can’t be suggested. Also, we can’t have single phasing protection by using MCCB. Hence, in this case, ‘Type 2’ coordination charts shall be referred to so as to make an appropriate selection.