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AC MCB vs. DC MCB: An In-Depth Comparison

AC MCB (miniature circuit breaker)
AC MCB (miniature circuit breaker)
Resource: https://www.ecmag.com

Both AC MCB and DC MCB breakers are designed to protect electrical circuits. However, as revealed in this AC MCB vs. DC MCB comparison, the two types of breakers are different in several ways. Buyers must, therefore, understand the variations between these two types of MCBs so they can make informed decisions. That’s what you will learn in this article: the AC MCB and DC MCB difference.


Before we can look at the AC DC MCB difference, it is important to understand the characteristic of each type of miniature circuit breaker. This will give you a better foundation to understand how they differ from each other. After that, we will look at their differences and suitable applications.

MCB for AC

An AC MCB is used to protect circuits against overcurrent in alternating current systems. These breakers are designed to safely disconnect the circuit when there is an overload or a short circuit, thereby averting damage to the circuit or load. The tripping current of an AC MCB can be either fixed or adjustable.

The AC MCB is available in a variety of designs. The most common type is the type B thermal-magnetic AC breaker, which uses a bimetallic strip and magnetic coil (solenoid) to detect overcurrents.

Because the current in an AC circuit is constantly changing, the design of the AC MCB must take this into account. This is one of the reasons why these are different from DC MCBs, as we will see shortly.

MCB for DC

These are miniature circuit breakers that have been built to work with direct current power systems. The main function of a DC MCB is to protect against overloads and short circuits, just like the AC type.

The DC MCB working principle is also similar to that of the AC MCB. However, because the direct current is constant, the DC breaker does not need to account for the changing current like its AC counterpart. This difference in design leads to a few others, which we will discuss below.

An example of a DC MCB circuit breaker
An example of a DC MCB circuit breaker
Resource: https://www.youtube.com/watch?v=eoeBnk95Vfs


Given the above information, what are the differences between AC MCB and DC MCB circuit breakers? To answer this question, we need to look at the key variations between these two types of MCBs based on their intended circuits or electrical systems.

AC MCB vs. DC MCB: Arc Extinguishing

The biggest difference between AC and DC MCB breakers is how they extinguish the electric arc that forms when contacts separate. In an alternating current circuit, the current changes direction many times per second, 60 or 50 times depending on the country.

This causes the arc to flicker on and off at a rapid rate each time the voltage rises to a peak and then falls to zero. As a result, the arc is quickly and easily extinguished by the breaker, without an elaborate mechanism being used, and the circuit is protected.

In a direct current circuit, however, the current only flows in one direction. This means that the arc can stay on for a much longer period before it is extinguished. It’s also more resistant to

To protect against this, DC miniature circuit breakers (MCBs) have special arc extinguishing chambers. This help extinguishes the arc by elongating as well as dissipating it.

AC MCB vs. DC MCB: Application

The AC MCB and DC MCB difference is also seen in the intended applications. AC MCBs are generally used for domestic or industrial purposes, in circuits where the current alternates.

On the other hand, DC MCB circuit breakers are used for renewable energy systems, such as solar power or wind turbines, where direct current is generated. They can also be used in cases where a battery is used as the power source, such as in a UPS system.

A DC MCB for solar energy may be used to protect a specific load or at the main circuits for the solar system.

AC MCB vs. DC MCB: Markings

The other difference between an AC and DC MCB miniature circuit breaker that we will look at is how they are marked. Generally speaking, an AC MCB will be marked with “Line” or “Load” to indicate where it should be placed in the circuit. DC MCBs, on the other hand, will be marked with “+” and “-“symbols to show the direction of the current flow.

Having said that, some miniature circuit breakers, both AC and DC, may not have any markings at all. These are non-polarity breakers that can be connected either way around in the circuit.

Polarity is important for DC MCB circuit breakers, as connecting them the wrong way around could cause damage to the breaker or the system as a whole. Non-polarity breakers are less likely to cause issues if they are installed incorrectly. These are suited for some applications such

DC miniature circuit breaker (MCB)
DC miniature circuit breaker (MCB)
Resource: https://www.youtube.com/watch?v=kRB7Z66brO0

Can I Use ac Breaker for DC?

No, you cannot use an AC MCB for a DC application and vice versa. This is because the design of the two types of MCBs is different, as we have seen.

The reason for this is that the arc extinguishing mechanism is different, and AC MCB breakers are not designed to protect against the longer-lasting arcs that can occur in DC circuits.

Using an AC MCB in a DC circuit can therefore lead to damage to the breaker or the circuit itself. It is always best to use the correct type of MCB for the intended application.


Both AC MCB and DC MCB are two types of circuit breakers that have been designed for different applications. An AC MCB is used in circuits where the current alternates, while DC MCBs are used in renewable energy, UPS systems, and other applications where direct current is generated.

The two types of MCBs differ in several ways. It is important, therefore, to use the correct type of MCB for the intended application, as using the wrong type can lead to damage to the breaker itself or the electrical system and its connected loads.

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