MCB Selection Guide | How to Select A Miniature Circuit Breaker?

11th Apr 2023

Overload of power or power surge can cause major damage to the electric circuit, appliances, and other property.

In order to prevent damage, MCB or miniature circuit breaker is used. As the name goes, it helps to break the flow of current in the circuit, thereby protecting against power overload.

However, there are different types and variations of MCBs available in the market. You need to choose the right one for complete protection.

In this guide, we will explain to you about miniature circuit breakers and help you to select the right device. 

What Is A Miniature Circuit Breaker?

TSB3-125 Miniature Circuit Breaker

A miniature circuit breaker, also known as a circuit switch breaker or MCB is an automatic electric switch designed to prevent electrical current from flowing when the input voltage exceeds the maximum allowable value. 

Its main function is to prevent current flow after an unpermitted fault is detected. These are used in various applications where sudden surges of electricity may result in damage to the equipment and appliances. 

These switches offer safety against the high risk of electric shock and short circuits. They work effectively in preventing the flow of any excessive amount of voltage to the circuit.

A miniature circuit breaker has two independent operational mechanisms. One of these mechanisms allows the electrical current to go through the circuit after detecting a fault and the other one relays the request to the relaying source to cut off the power supply when the detected fault is found. 

The working mechanism of these appliances works very simply and involves a simple switch to flip the switch to activate the working mechanism. Once the fault is detected, the bimetallic strip heats and bends, thereby tripping the switch. It breaks the current supply. 

Once it cools down and there is no fault, it goes back to the normal position, thereby allowing the current to flow. It is important for any business to be safe from any type of overload, which can result in catastrophic damage to their business and property. 

Thus, it is imperative for a company to purchase a miniature circuit breaker to provide complete protection from overloads and short circuits. Some of these products have built-in surge protection, which is designed specifically to meet the requirements of both normal and overload use in the workplace. 

How to Select a Miniature Circuit Breaker?

Here are some of the things you need to consider in order to select a miniature circuit breaker

  • Rated Current: It is the amount of current the circuit can handle. It can withstand currents from 0.5A to 125A. So, you need to check the power supply of the circuit and accordingly choose an MCB as per the power. 
  • Number of Poles: There are different types of MCBs available as per the number of poles, i.e. single, single pole and neutral, double, triple, and four poles. You need to consider the phase and neutral to choose an MCB.
  • Tripping Characteristics: It shows the tripping time required by the MCB. The tripping range differs from one MCB to another. So, you need to check the tripping class of the device. You can choose from the B curve, C curve, D and K curve, and Z curve. 
  • Rated Operational Voltage: It is the voltage required for the MCB to function. It is the maximum value. As different MCBs have different operational voltages, you need to choose them accordingly.
  • Breaking Capacity: It is the current that the device can carry and break. You need to choose a low-breaking capacity MCB for household use.
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