What is MCB ?

 A miniature circuit breaker (MCB) automatically switches off the electrical circuit during an abnormal condition of the network means in overload condition as well as faulty condition. Nowadays we use an MCB in a low voltage electrical network instead of a fuse. ... MCB is much more sensitive to overcurrent than a fuse

MCBs or Miniature Circuit Breakers are protective electromagnetic devices that act as a switch in a circuit. They automatically open the circuit whenever they sense the current passing over the circuit has crossed a certain limit or value. The device can also be used as a normal on and off switch manually. 

MCBs are also known as time delay tripping devices which trip and shut down the system whenever there is an overcurrent flowing for a longer period of time and there is a danger to the entire circuit. However, in the case of short-circuits, these devices can trip and stop the power supply within 2.5 milliseconds.

In an electrical system ‘Fault’ is the condition which arises due to the malfunctioning of some component or wrong electrical practice. A fault may lead to a very dangerous situation such as explosion & fire if not cleared timely, not only this, the amount of time for which fault remains in the system, it continuously deteriorates the system health causing high energy losses resulting in increased thermal stress upon the system. Faults are hazardous to the system & require to be cleared at the earliest thus, there is a need for such a device that not only is capable of clearing the fault but also has a lower opening time in order to save the let-through energy & minimize the thermal stress.

type of curve/applications the MCB is of 3 types:

B Curve: This type of MCB has a lower short circuit trip zone and can be used for Resistive/ Lighting loads, for example, lights, heaters, etc.

C Curve: These MCBs have a higher short circuit tripping zone and can be useful for the inductive type/motor loads, for ex: AC, Refrigerator, etc.

D Curve: These MCBs have a very high short circuit tripping zone and are generally used for the loads which draw a very high starting current such as Sodium Lamps. 

2 kinds of fault which disturb the system often are:

Overload: An overload is a fault condition that arises in a system when a circuit draws a higher current than its rating. For example from a 6A socket if we draw 10A current the condition is said to be overload.

Short Circuit: This is a condition in which an extremely low resistance path is created due to an accidental or intentional connection between 2 or more conductors which leads to the sudden increase of current to its peak value and voltage getting minimized to an extremely lower magnitude.

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.

What is RCCB ?

 Residual Current Circuit Breaker (RCCB) is an important safety measure when it comes to the protection of electrical circuits. It is a current sensing device, which can automatically measure and disconnect the circuit whenever a fault occurs in the connected circuit or the current exceeds the rated sensitivity

Principle behind RCCB

RCCB works on the principle of Kirchhoff’s law, which states that the incoming current must be equal to the outgoing current in a circuit. RCCB thus compares the difference in current values between live and neutral wires. Ideally, the current flowing to the circuit from the live wire should be the same as that flowing through the neutral wire. In case of a fault, the current from the neutral wire is reduced, the differential between the two known as Residual Current. On spotting a Residual Current, the RCCB is triggered to trip off the circuit.

A test circuit included with the Residual Current device ensures that the reliability of RCCB is tested. When the test button is pushed, the current starts to flow through the test circuit. As it creates an imbalance on the neutral coil of the device, the RCCB trips and supply is disconnected thereby checking RCCB’s reliability.

Benefits of RCCB

Provides protection against earth fault as well as any leakage current

Automatically disconnects the circuit when the rated sensitivity is exceeded

Offers the possibility of dual termination both for cable and busbar connections

Offers protection against voltage fluctuation as it includes a filtering device that guards against transient voltage levels.

 Sensitivity of RCCB

A human being is able to sustain an electric shock to the extent of 30 mA. While up to 10 mA may just evoke a prickling sensation, 10 mA onwards may lead to muscular contraction, further leading to a respiratory paralysis at around 30mA. RCCBs are therefore designed to look for small changes in residual current. In cases where protection from fire is sought, RCCBs are also used to track higher changes in residual current of up to 300mA.

Limitations of RCCB

While RCCB has many advantages, it has some limitations as well:

RCCB does not guarantee to operate if none standard waveforms are generated by loads. It’s mainly because RCCB is designed to operate on normal supply waveforms.

There might be some unwanted tripping of RCCB. It’s mainly because whenever there are sudden changes in electrical load, there can be small current flow to earth, especially in old appliances.

RCCB does not protect from current overload. It has been designed to protect only when the live current and neutral current are different. However, a current overload cannot be detected.

RCCB does not protect against line-neutral shocks. It’s mainly because the current in them is balanced. The current gets balanced as both terminals are held together.

RCCB does not protect from the overheating that strike if conductors are not properly screwed into terminals.

 Classification of RCCB

RCCB is of two types; the 2 Pole RCCB and 4 Pole RCCB.

2 Pole RCCB: This is used in case of a single-phase supply connection that has only a live and a neutral wire.

4 Pole RCCB: This is used in case of a three-phase supply connection.

Rating from 10 Amp ….100 Amp

Sensitivity 30,100,300 m Amp

RCCB is therefore extremely important in providing real-time protection for circuits. In industries and high voltage commercial setups especially, its importance cannot be undermined as there is always a risk of shocks and accidental deaths on account of it. At C&S Electric, we offer Wintrip RCCB, a state-of-the-art product fit for industrial, residential, and commercial applications. C&S RCCBs conforms to IEC 61008 – 1 and is used for both control and isolation of electrical circuits. Being a respected global brand for power management products for over 50 years, with C&S Electric you can rest assured knowing that you are in safe hands.