How to Select the Motor Protection Circuit Breaker?

30th May 2022

If you want to select a motor protection circuit breaker, first, you have to determine the total nameplate rated current for your motors. This should be based on the maximum amount of current that can be handled by a single breaker. 

Next, determine the Withstand capacity of the breaker. This is usually the breaker’s capacity to tolerate the highest run current for a short period of time. For example, if your motor is rated at 2.5 A and your breakers have an 8 A Withstand capacity, you will need to select a breaker with a capacity of at least 8.4 A.

When purchasing motor protection circuit breakers, it is important to look at the thermal and magnetic release columns to understand the values for each. The thermal and magnetic release columns will give you an idea of the protection that you should look for. 

If you want to know how to select the motor protection circuit breaker, continue reading this article. 

What Is Motor Protection Circuit Breaker?

A Motor Protection Circuit Breaker is a simple electromechanical device used to protect electrical motors from overload, fluctuations in input current, line faults, and phase loss in three-phase motors. 

The Circuit Breaker saves space and provides fuseless protection, switching off the motor immediately if there is a short circuit. They may also include features such as a thermal delay or automatic reconnection when the motor cools.

An MPCB is specially designed to protect electric motors from overload and overheating. The thermal contact protects against excessive electric currents. An oversized MPCB cannot detect over-current conditions, and the motor will fail to start. An MPCB is a very important part of the electrical system. 

The MPCB has an adjustable bimetallic strip that provides overload protection. The bimetallic strip adjusts between two set values, 40% and 100% of rated current. An MPCB with MPCB backup protection prevents both overload and short-circuit conditions. 

How to Select the Motor Protection Circuit Breaker?

Motor protection circuit breakers are important to the safety and efficiency of your motor. They need to function properly in all conditions, from the initial installation to warranty replacement. By selecting the right breaker for your application, you will avoid costly downtime, enhance motor efficiency, and ensure the continued safety and reliability of your motor. 

When purchasing a motor protection circuit breaker, consider the following criteria: voltage and overload capacity. If the motor cannot sustain the voltage, it will shut down. Choose a motor protection circuit breaker that has an overload capacity of 5,000 volts. A properly functioning motor protection circuit breaker can handle a range of voltages. You should also consider the electrical life of your motor and its operating conditions. These factors will make the selection process much simpler.

It’s important to choose the right MPCB for your application. A simple MCB is not enough protection for an electric motor, and using it alone is risky. PCBs are the best way to protect your electric motor from overcurrent conditions. They’re easier to select than MCBs, and the motor ratings are clearly listed. You can also find a specialized MPCB for your application.

When choosing an MPCB, always consider the nameplate current of the electric motor. Although the nameplate current is the maximum operating current of the electric motor, the actual operating current may be much less, particularly when it’s not fully loaded. 

The current nameplate value of the MPCB is important as it’s how much inrush current a motor will draw during startup or part-load operation. A 20 amp motor may draw a lower current during part-load operation and trip when it reaches the full load. The best MPCBs will take into account these factors to help prevent this type of electrical disaster from occurring.

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