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How to Select a Suitable DC MCB?

What is the Definition of a Miniature Circuit Breaker?

An MCB (miniature circuit breaker) or DC MCB is a switch that closes, carries, and breaks a circuit. It can open the circuit if the circuit current exceeds a certain threshold. You can usually use an isolator with a fuse in place of miniature circuit breakers.

The Functioning Principle of the DC MCB

An MCB is a switch that changes fault current or carries rated current. When the circuit current exceeds a defined amount or limit, these devices can automatically cut the circuit. You can manually switch on or off the MCB like standard switches whenever necessary.

Trip/Automatic Operation

Magnetic Trip and Thermal Trip are Two Techniques to Obtain MCB

The current passing through the bimetal will cause the temperature of the bimetal to rise during an overload. The heat associated with the temperature rise in the bimetal induces bending because of the expansion of the metal. The trip latch is released, and the current separates the contacts due to the deflection.

Magnetic tripping is quite active in short circuits or difficult overload situations. The light spring holds the slug in place under normal working conditions because the coil’s magnetic field not being strong enough to attract the latch. When a fault occurs in the circuit and current runs through it, it forms a magnetic field by the coil that is strong enough to pull the spring, keeping the slug in place, causing the slug to move and the tripping mechanism to activate.

The majority of MCBs use a combination of thermal and magnetic tripping mechanisms. When the contacts begin to separate in both actions, it creates an arc. Then, it drives the arc into an arc divider through an arcing route. Arc chutes are another name for arc divider plates. The contacts create the arc into a sequence of arcs, taking energy simultaneously. As a result, the arrangement will get interrupted.

MCBs Come in a Variety of Shapes and Sizes

Alternating Current Miniature Circuit Breaker (AC MCB) and Direct Current Miniature Circuit Breaker (DC MCB) are the two most common miniature circuit breakers. In terms of parameters, there isn’t much of a difference. The difference between AC and DC MCBs is that Switching off DC with a DC MCB is more complex than with an AC MCB. The AC MCB relies on the zero crossing of the AC to operate, whereas the DC MCB relies solely on the mechanical structure. When you compare it to AC circuits, DC circuits require the MCB to open it faster, increasing the MCB’s complexity. Professionals classify the two types of MCBs as polarity/polarized and non-polarity/non-polarized, respectively.

AC MCB with Polarity 

For the MCB to function effectively, you must connect the power supply to the “Input/Line” terminal. You must link the load to the “Load/Output” terminal, as indicated by the manufacturer. If you misconnect the MCB, it will most likely fail to protect the circuit when it needs.

AC MCB with Non-Polarity

Manufacturers do not include any markings on non-polarity AC MCBs. You must connect the load to one terminal and the electricity to the other.

DC MCB with Polarity

You can use the Polarity DC MCB: “+” and “-” to indicate the polarity of DC MCBs. If you misconnect the polarity DC MCB, difficulties may arise. The MCB will be unable to turn off the current and extinguish the arc during an overload or short circuit conditions, causing the circuit breaker to burn out. The arc is pulled from the contact and into the arc extinguishing chamber by a tiny magnet in the polarity DC MCB. The magnet will lead the arc out of the arc extinguishing chamber and into the MCB mechanism if the current running through the device is in the other direction, harming the equipment.

DC MCB with Non-Polarity

The “+” and “-” indications are not present on non-polarity DC MCBs. You can use these MCBs safely as load isolators to protect the circuit in the case of a fault current, regardless of the circuit’s current direction. The current must often be reversed as needed, especially in circuits with energy storage batteries, and non-polarity DC MCBs can efficiently offer protection. Simultaneously, you can also opt for DC MCB that uses solar energy to direct current. You can visit websites like GEYA.net to buy the best DC MCBs that use solar energy to load power. The usage of solar energy in Australia is becoming quite popular because of its several benefits.

When selecting AC or DC MCB with or without polarity, you must choose DC MCB as it provides additional security.

MCB’s Parameters

Except for rated voltage and current, there are other vital parameters: rated overload current, ultimate short-circuit braking capability, and characteristic trip curve.

Overload Current Rated

The current will exceed the current that the circuit can withstand if there are too many loads. To protect the wires and other devices, the MCB should turn off the load in this circumstance.

The rated current that every MCB has is from 0.5A to 125A. Therefore, you must select the D curve type MCB to reduce highly inductive loads. That is the best fit for all homes and small offices.

Capacity to Break Short Circuits at the Highest Level

If a defect arises in the circuit, it will short-circuit, and the current will surge hundreds to thousands of times its average level. To minimize appliance damage or fire incidents, the MCB must disconnect the power quickly. As a result, the MCB must be able to interrupt the fault current while operating at the rated short-circuit current, and it must accomplish the same within the stated time limit.

For all domestic appliances, the Type C capacity is the best fit. It can handle up to 5 to 10 times of current flow compared to the normal ones.

The Three Types of DC MCB

DC MCB of type B:

The design of the MCB allows it to trip at a current of 3 to 5 times the rated current. Typically, you can utilize these MCBs for inductive or resistive loads with low switching surges. As a result, they are appropriate for household and light business use.

DC MCB of type C:

The design of the MCB allows it to trip at a current of 5 to 10 times the rated current. Typically, you can utilize these MCBs in fluorescent lights and small motors with high inductive loads and high switching surges. As a result, they’re appropriate for industrial and commercial applications that require much induction.

DC MCB of type D:

The design of the MCB allows tripping at a current of 10 to 20 times the rated current. Professionals typically employed it for highly high inductive loads with high surge currents. As a result, X-ray machines, UPS systems, huge winding motors, and industrial welding equipment can all benefit from them.

Products Available

There are many products available on the GEYA.net official website that you can buy. Some products are listed below:


This DC circuit breaker is the best fit for homes that can use up to 250V with a rated current of 63A line. It can help in protecting overload, short circuit, and infrequent operation. It has an indicator function, transparent cover and can adapt to broader utilization.


This product can also hold up to 500 volts of current with a 63A rated current. It also provides sufficient protection from short circuits, overload, and infrequent operations. You can use DC applications like photovoltaic systems, communications, and many more.


Hence, while choosing a suitable DC MCB, first, you should determine the circuit’s total current. Then, you should select the proper MCB. The current rating of MCBs should not be greater than the cable current carrying capacity. It should also be greater than the maximum current that the user expects the system to maintain.

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