MCCB is the device which is manufactured as an integral inner supporting and enclosed housing of insulating material. It is required for making, carrying and breaking currents between separate contacts under normal circuit condition and abnormal circuit condition such as those of overload condition and short circuit condition. MCCBs provide protection to low-voltage distribution system.
Quenching the arc in air inside the moulded case, the MCCBs interrupt current with 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 separation 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 abnormalcondition. 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 a wire since it needn’t bother with a substitute once an over-burden is taken note. Dissimilar to a 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 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 has 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 or the two different trip elements will protect the circuit against situations such as:
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.
It is the conditiondue to an intentional or unintentional low impedence 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 the 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 are 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.
Now days MCCBs are available with 2 kinds of release, one is with thermal-magnetic &other is microprocessor release.
Thermal-magnetic uses the principle of bimetal and electro-magnetic 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 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 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
Wrong Selection of MCCB:
For few special applications, manufacturers recommend to use MCCBs dedicated to that application. For Ex. For motor back up protection there is a requirement for overload protection of motor, it is required to match the overload settings of MCCB with that of motor. This solution assures no damage to the motor in case of motor overloading. However life expectancy of contactor as per the circuit design is considered better than that of MCCB. Hence this combination will give much lesser life, thus it can’t be suggested. Also we can’t have the single phasing protection by using MCCB. Hence, in this case ‘Type 2’ coordination charts shall be referred so as to make an appropriate selection.