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Understanding Type B MCB (Miniature Circuit Breaker)

Type B MCB in a domestic distribution box
Type B MCB in a domestic distribution box
Resource: https://youtu.be/cGCkXtYhwd8

Do you often come across the terms ‘type A MCB’, ‘type B MCB’, and so on but have no clue what they mean? If yes, then don’t worry because you are not alone. Many people are not aware of the different types of MCBs (Miniature Circuit Breakers) and their functions.

In this article, we will be discussing B-type MCB in detail. We will also talk about what they are used for among other things. To start us off, what does type B MCB mean?

Type B MCB Meaning

To protect low-voltage electrical circuits, type B MCB is often used. The breaker interrupts the circuit before when it detects a fault current or overcurrent. That way, any damage to the wiring or appliances due to an overload of current or unexpected short circuit is prevented.

MCB stands for mini circuit breaker, and B MCB type is just one of the many types available. As its name suggests, a miniature circuit breaker is a lot smaller than the traditional air circuit breakers that are found in some electrical systems.

Type B miniature circuit breakers belong to a class of MCBs that are classified according to their tripping curves and tripping characteristics. Class B MCBs trips are characterized by their quick response to short-circuit currents, which makes the breaker highly sensitive to electrical faults.

Speaking of the type B MCB curve, here is what it looks like when compared to other miniature circuit breakers:

Type B MCB tripping curve compared to that of other breakers
Type B MCB tripping curve compared to that of other breakers
Resource: https://electrical-engineering-portal.com

Type B MCB Tripping Curve

The type B MCB curve is designed to offer protection against small overloads and sudden changes in current. As such, these types of miniature circuit breakers are most suited for low-current electrical circuits or loads. Below is more about these the tripping curve of these types of miniature circuit breakers:

The type B MCB curve consists of two upper sections, as can be seen in the graph, the thermal protection curve. This curve is designed to offer protection against sustained overcurrents. The lower section of the graph is the magnetic protection curve which is designed to offer protection against sudden changes in current such as short circuits.

MCB Thermal Trip

The thermal protection curve of the type B curve MCB is designed to offer a delayed overload trip using a bimetallic strip tripping mechanism. However, if the overload is sustained, then the thermal protection will cause the breaker to trip.

MCB Magnetic Trip

The type B MCB magnetic trip curve shows the behavior of the breaker when there is a sudden change in current. The trip curve is designed such that the breaker will trip for small changes in current. The type B MCB tripping curve is designed to offer protection against short circuits.

Type B MCB tripping characteristics and mechanism illustrated
Type B MCB tripping characteristics and mechanism illustrated
Resource: https://www.youtube.com/watch?v=oYLIpN4RwEg

Type B MCB Tripping Characteristics

A type B MCB works by sensing the current flowing through the circuit and trips when it exceeds the preset threshold. The tripping mechanism is achieved by the use of a bimetallic strip that is located inside the MCB as well as a magnetic coil or solenoid.

The type B MCB tripping characteristics are summarized below:

  • The type B curve MCB is normally built to trip 3 to 5 times its rated current. That means a 10A breaker will trip when the current exceeds 30A to 50A.
  • The type B MCB has a very fast tripping time for short circuits, in the region of 0.04 to 13 seconds for overloads.
  • The type B MCB is designed to protect cables and conductors from overheating due to overload or short-circuit conditions. It is not suitable for the protection of motors and transformers.
Using MCB type B in an electrical panel
Using MCB type B in an electrical panel
Resource: https://www.youtube.com/watch?v=M6kjS-_Ivp4

MCB Type B or Type C?

The two most common types of MCBs are type C and type B. Although they operate similarly, some key differences between the two make them suitable for different applications.

The type C MCB is designed to offer protection against large overloads, such as those found in industrial applications, which makes them suitable for circuits with inductive loads and possible inrush currents.

The B-type MCB, on the other hand, is designed to offer protection against small overloads and sudden changes in current. This makes them ideal for use in circuits with resistive loads, such as lights that are non-inductive and have a low or no inrush current.

Which one should you use? Whether to use an MCB type B or type C depends on the application. If you need an MCB for an industrial circuit with high currents and inductive loads, then a type C MCB is the way to go. If you need an MCB for a domestic circuit with resistive loads, then a type B MCB will do the job just fine.

Type B MCB uses in residential electrical systems
Type B MCB uses in residential electrical systems
Resource: https://youtu.be/WNe1xHlI5i4

Type B MCB Uses

Type B MCBs are used for the protection of electrical circuits against overload and short-circuit currents. Type B MCBs are suitable for use in a wide range of applications. Some of the most common type B MCB uses include:

Domestic applications: Type B MCBs are commonly used in domestic applications such as homes, apartments, and so on. They offer adequate protection to electrical circuits against overload and short-circuit currents.

Commercial applications: Type B MCBs are also suitable for use in commercial applications such as offices, shops, and so on. They offer a quick response to both overload and short-circuit currents, making them ideal for use in these applications.

Conclusion

The type B MCB is a mini circuit breaker that is used for the protection of low-current electrical circuits. These MCB types belong to a class of MCBs that are classified according to their tripping characteristics. Type B MCBs are characterized by high sensitivity to changes in current to trip when levels exceed preset limits and pose a danger to cables and other parts of the electrical system or even appliances.

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