MCCB: Applications & Advantages

Electricity has become one of the most important aspects of today’s living, and people’s dependency on it is increasing day by day. Thus, it has become necessary to take smart actions to save electric power. Thus, electrical devices and controlling of flow of current is a basic move that needs to be taken. With the exceptional flow of current and short circuit, the chances of extreme damage to the circuit increase day by day. To prevent faulty situations, LVS (Low Voltage Switchgears) are used to protect the injuries. Amongst these devices come MCCB.

What Are MCCBs?

MCCB is known as Moulded Case Circuit Breaker. The MCCB is used in places where adjustable tripping is required. It is essentially used for high current applications and features a manually operated switch for tripping the circuit. It is majorly used for both low and high breaking capacity requirements, mainly industrial. The electric device mentioned here is manufactured as an electrical protection device and is used to protect the electric circuit from excessive current, which is the reason for causing a situation of overload or short circuit. 

MCCB has two arrangements, where one is for the over-temperature, and the other one is for over current. It has a bimetallic contact, which with the temperature change, expands and contracts. During the normal working conditions, the bimetallic contact allows the current to free flow through the circuit. However, in case the current goes beyond the upper predefined limit, the bimetallic contact will get warm and expand till the time they get open. Due to this, the circuit gets disconnected from the main supply, protecting the equipment from damage.

Specifications of MCCBs 

When it comes to electrical protection, miniature circuit breakers (MCBs) and molded case circuit breakers (MCCBs) are two commonly used devices. While both devices serve the same purpose of protecting electrical circuits from overloads and short circuits, there are significant differences between the two. 

The difference between MCB and MCCB lies in their current-carrying capacity and tripping characteristics. MCBs are designed for low-current applications, while MCCBs are suitable for high-current applications. 

In this section, we will delve deeper into the specifications of MCCBs and explore their features, construction, and applications. Here are some key specifications of MCCBs to keep in mind:

1. Current rating

MCCBs are designed to handle higher currents than MCBs, typically ranging from 10A to 2,500A. The current rating is one of the most important specifications to consider when selecting an MCCB, as it determines the amount of current the breaker can safely interrupt without sustaining damage.

2. Breaking capacity

The breaking capacity of an MCCB refers to its ability to interrupt current flow during a fault condition. The breaking capacity is specified in terms of kA, which represents the maximum amount of current the MCCB can interrupt safely without damaging its internal components.

3. Tripping characteristics

MCCBs are designed with adjustable tripping characteristics, which allows for customization of the device's response to overloads and short circuits. The tripping characteristics of an MCCB can be either thermal or magnetic, depending on the type of overload being protected against.

4. Construction

MCCBs are typically constructed with a molded case, which provides protection against environmental factors such as dust and moisture. The internal components of the MCCB are housed in a thermoset or thermoplastic material, which provides mechanical strength and insulation.

5. Accessories

MCCBs can be customized with a range of accessories to suit specific applications. These accessories can include auxiliary switches, shunt trips, under-voltage releases, and more.

Components of Molded Case Circuit Breakers

Molded case circuit breakers (MCCBs) are essential devices for protecting electrical circuits from overloads and short circuits. They are widely used in residential, commercial, and industrial settings due to their reliability, durability, and flexibility. 

MCCBs consists of several components that work together to ensure proper circuit protection. In this section, we will explore the key components of MCCBs and their functions. Here are some essential components of MCCBs to keep in mind:

1. Frame

The frame of an MCCB is the outer casing that houses all the internal components. The frame is typically made of molded plastic or metal and provides mechanical strength and protection against environmental factors such as dust and moisture.

2. Operating mechanism

The operating mechanism of an MCCB is responsible for opening and closing the circuit breaker. It typically consists of a handle or lever that is used to manually operate the device, as well as a mechanism for tripping the breaker automatically in the event of an overload or short circuit.

3. Trip unit

The trip unit is the heart of an MCCB, responsible for detecting and interrupting current flow during an overload or short circuit. The trip unit can be either thermal or magnetic, depending on the type of overload being protected against. The trip unit is typically adjustable, allowing for customization of the device's tripping characteristics.

4. Contacts

The contacts of an MCCB are responsible for making and breaking the electrical connection in the circuit. The contacts are typically made of a high-conductivity material such as copper or silver and are designed to withstand high current and voltage levels without sustaining damage.

5. Arc extinguishing system

During the interruption of an electrical circuit, an arc is generated between the contacts of the breaker. The arc extinguishing system of an MCCB is responsible for quickly extinguishing the arc to prevent damage to the device and surrounding equipment. The arc extinguishing system can be either magnetic or thermal, depending on the type of breaker.

6. Accessories

MCCBs can be customized with a range of accessories to suit specific applications. These accessories can include auxiliary switches, shunt trips, under-voltage releases, and more.

Advantages of the MCCB

Molded Case Circuit Breakers (MCCBs) are widely used in a variety of electrical applications due to their numerous advantages over other types of circuit protection devices. MCCBs provide reliable and durable protection against overloads and short circuits, and they offer a range of customization options to suit specific applications. 

In addition, MCCBs have several key advantages over other circuit protection devices, such as miniature circuit breakers (MCBs) and fuses. Some of these MCCB advantages include higher current ratings, adjustable tripping characteristics, and improved safety features. 

In this section, we will delve into the many advantages of MCCB and why they are the preferred choice for many electrical applications. Whether you are a homeowner, electrician, or industry professional, understanding the advantages of MCCB is essential for selecting the right circuit protection device for your needs.

1. Thermal Overload

Molded Case Circuit Breakers (MCCBs) offer several advantages over other circuit protection devices, one of which is thermal overload protection. Thermal overload protection is a critical feature of MCCBs, as it prevents overheating of electrical equipment and wiring due to excessive current flow.

Thermal overload protection is achieved through the use of a bimetallic strip or a heater element within the MCCB's trip unit. The bimetallic strip or heater element is designed to heat up when current flows through it, causing it to bend or trip the breaker. This action occurs when the current flowing through the MCCB exceeds a certain level, typically called the "thermal trip rating."

The thermal trip rating can be adjusted on most MCCBs to suit the specific application. This adjustment allows the user to customize the MCCB's tripping characteristics, ensuring that it provides the appropriate level of protection for the equipment or wiring is protected. For example, an MCCB protecting a motor might be set to trip at a higher current level than one protecting lighting circuits, as motors typically have higher inrush currents.

One of the key advantages of MCCB is its ability to provide precise and consistent thermal overload protection. Unlike fuses, which must be replaced after tripping, MCCBs can be reset after tripping, allowing for the uninterrupted operation of the protected equipment. This feature also allows for easier troubleshooting, as the user can quickly identify the cause of the trip and take corrective action.

2. Short-circuit Condition

Short-circuit conditions can cause significant damage to electrical equipment, and it is important to have reliable protection against them. Molded Case Circuit Breakers (MCCBs) is one of the most effective circuit protection devices for short-circuit conditions and offer several MCCB advantages and disadvantages over other types of protection devices.

Short-circuit conditions occur when there is a direct connection between two conductors with a low-impedance path. This can cause a sudden surge in current flow, which can damage electrical equipment and cause fires. MCCBs are designed to detect short-circuit conditions and quickly interrupt the flow of current to prevent damage.

The trip unit of an MCCB is designed to detect short-circuit conditions and trip the breaker within milliseconds to prevent damage to the protected equipment. The tripping mechanism of MCCBs is typically a magnetic trip element, which uses the magnetic field generated by the short-circuit current to trip the breaker. This rapid tripping action helps to prevent damage to the equipment and minimize downtime.

Another advantage of MCCBs for short-circuit conditions is their high interrupting capacity. Interrupting capacity refers to the maximum amount of short-circuit current that an MCCB can interrupt safely without damage. MCCBs have higher interrupting capacities than other circuit protection devices, such as fuses and miniature circuit breakers (MCBs), making them better suited for protecting high-powered electrical equipment.

3. Ground Fault condition

Ground faults can be a serious safety hazard in electrical systems, and it is important to have reliable protection against them. Molded Case Circuit Breakers (MCCBs) are one of the most effective circuit protection devices for ground faults and offer several advantages over other types of protection devices. 

A ground fault occurs when an electrical conductor comes into contact with a grounded surface, such as the metal casing of a machine. This can cause a leakage of current to the ground, which can be hazardous to people and equipment. MCCBs are designed to detect ground faults and quickly interrupt the flow of current to prevent injury or damage.

The trip unit of an MCCB is designed to detect ground faults and trip the breaker within milliseconds to prevent injury or damage. The tripping mechanism of MCCBs for ground faults is typically a residual current device (RCD), which monitors the current flowing through the phase and neutral conductors and detects any imbalance in the current flow. If an imbalance is detected, the RCD trips the MCCB to interrupt the current flow and prevent injury or damage.

Another advantage of MCCBs for ground faults is their ability to provide selective coordination. Selective coordination refers to the ability of a circuit protection system to selectively trip only the device that is closest to the fault while leaving other devices intact. This ensures that only the faulty circuit is de-energized, minimizing downtime and maximizing safety.