Interrupting Ratings: Air Rated Breakers Explained

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In summary, air rated breakers do have interrupting ratings that range from 22 to 65 kA. This rating is important for power equipment as exceeding it can cause the contacts to become fused, putting lives and equipment at risk. The interrupting rating is discussed in detail in a commercial electrical wiring class, but there is no information on what exactly happens when it is exceeded. Unfortunately, the source of this information, Michael Bell, has passed away.
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Josh111
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do air rated breakers still have interrupting ratings?
 
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  • #2
Yes, of course they do. I work with several types of breakers with interrupt ratings from 22 to 65 kA. It's an important rating for power equipment because exceeding it can cause the contacts to become fused, rendering the breaker useless and putting lives and equipment at risk.
 
  • #3
I want to thank you for post regarding the interrupting rating because I am currently in a class on commercial electrical wiring and there is a large section on interrupting rating for circuit breakers in our book covering things like how they are tested and the various ways to install breakers in series assemblies with main and branch, but for some odd reason the book fails to detail what exactly happens when a short circuit actually exceeds a breaker's interrupting rating.

I naturally assumed that the circuit breaker would fail in some respect, but couldn't find any reference to exactly what the outcome might be besides a broken breaker. So thank you for your post.

Any more details you might add would be appreciated regarding the interrupting rating and what happens when a short circuit exceeds the breakers rating.
 
  • #4
Unfortunately, Negitron (Michael Bell) died in September.

There was a note about this on this page, but it has now gone.
 
Last edited:

1. What is an interrupting rating for air rated breakers?

An interrupting rating for air rated breakers is the maximum amount of current that the breaker can safely interrupt without causing damage. It is typically measured in kiloamps (kA) and is an important factor to consider when selecting a breaker for a specific application.

2. How is the interrupting rating determined for air rated breakers?

The interrupting rating for air rated breakers is determined through rigorous testing procedures by the manufacturer. These tests involve simulating different fault conditions and measuring the ability of the breaker to safely interrupt the current flow. The results of these tests are used to assign a specific interrupting rating to the breaker.

3. What is the difference between short-circuit and fault current?

Short-circuit current refers to the maximum amount of current that can flow through a circuit when there is a direct connection between two points of different potential. Fault current, on the other hand, refers to the current that flows when there is an unintended path for current to flow, such as through a faulty component or damaged insulation. Both of these currents are important to consider when determining the interrupting rating for a breaker.

4. How does the interrupting rating affect the selection of a breaker?

The interrupting rating is a crucial factor to consider when selecting a breaker for a specific application. If the interrupting rating of the breaker is not high enough, it may not be able to safely interrupt the current during a fault or short-circuit event, potentially causing damage to the breaker or other equipment. It is important to choose a breaker with an interrupting rating that exceeds the expected fault or short-circuit current in the circuit.

5. Can the interrupting rating of a breaker be increased?

No, the interrupting rating of a breaker cannot be increased. It is determined by the manufacturer during testing and cannot be changed. However, it is possible to select a breaker with a higher interrupting rating to ensure safety and reliability for a specific application.

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