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Understanding Circuit Breaker Ratings and Its Specification

Written by Edwin Jones / Fact checked by Andrew Wright

circuit breaker ratings

You would be wrong if you thought that circuit breaker ratings only refer to amperage ratings. There are other specifications as well, such as the voltage, current frequency, and continuous current. You can read the details below to get an idea about these ratings.

Circuit Breaker Ratings and Specifications

purpose-of-a-circuit-breaker

Generally, the performance of a circuit breaker is based on its ratings and specification. This means that by knowing the standard circuit breaker ratings, you can be protected from electrical problems.

The rating of circuit breaker is expressed in the nameplate on the device itself. This nameplate may indicate the voltage rating, frequency rating, current rating, and more. If you wonder what these are, here are some explanations of each below.

1. Voltage Rating

The circuit breaker voltage rating refers to the highest RMS voltage (Root Mean Squared) for which it is built. Some circuit breakers have more than one voltage number on their nameplate. You can tell the actual voltage rating of the breaker by identifying the highest voltage on the list.

2. Frequency Rating

Frequency rating specifies the operating frequency of a circuit breaker. Normally, typical circuit breaker sizes are rated 50 Hz or 60 Hz and are occasionally used in DC or direct current. Using a circuit breaker that is not within its operating frequency may cause a temperature rise and damage to the unit.

3. Continues Current Rating

Continuous current rating is the highest current a circuit breaker can take continuously on an operating frequency while maintaining its good condition. This rating reflects the breaker’s thermal design in that the device must not exceed its rated temperature increase.

4. Breaking Capacity

There are two types of breaking capacity, the Symmetrical and Asymmetrical kind. Each has its own characteristics.

  • Symmetrical breaking capacity

Symmetrical breaking capacity defines the circuit breaker’s symmetrical current and voltage recovery. It is the maximum RMS amount of an AC component of a short circuit current when the breaker contacts separate.

  • Asymmetrical breaking capacity

Asymmetrical breaking capacity defines the circuit breaker’s asymmetrical current and voltage recovery. It is the RMS amount that refers to the sum of AC and DC components of a short circuit current at the moment the breaker contacts separate.

The asymmetrical breaking current is higher than the symmetrical one.

5. Making Capacity

The maximum current that a circuit breaker can conduct at the point of closure is its making capacity. This specification applies to short circuits when the breaker contacts close.

6. Operating Sequence

The circuit breakers rated operating sequence refers to the speed with which they can open and close within a certain period of time. Common sequences include O-0.3s-C0-15s-CO and O-0.3s-CO-3 minutes-CO.

7. Short-Circuit Current Rating

The short circuit current rating (SCCR) refers to the circuit breaker maximum RMS current that it may carry without taking any external damage.

This measurement is often listed in kA (kiloampere). SCCRs are useful in determining the safety of equipment against fault currents. Many machines such as elevators, motors, and ACs in industrial zones require these measurements.

8. Short Circuit Withstand Capacity

The short circuit withstand capacity or ultimate breaking capacity (or kA) refers to the maximum current of a power circuit breaker that it can take instantaneously on a short circuit without failure. Using the wrong kA rating can lead to fires and even death.

Watching this following video by Electrical Engineering Planet will give you an understanding of the Schneider circuit breaker rating lists. Pay much attention as he explains the different types of specifications located on the brand’s product nameplate.

Furthermore, you can also look for a circuit breaker ampere ratings table—specifically with the brand and type of circuit breaker you need. This table will give you the circuit breaker specifications to identify the device for your application.

Conclusion

The purpose of a circuit breaker is to keep your home electrical system safe, so it is good to consider finding the appropriate breaker ratings required for your home.

If you are unsure what device you should use in your application, it is better to consult or at least search for a circuit breaker sizing chart online.

If you find this article helpful, you can share this on your social media to spread the information about circuit breakers.

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