Short Circuit Test on Circuit Breaker

[KRC83]

When Low Voltage MCCB say 200A 22kA 240AC is tested for short circuit test can anyone provide below information
1. How to calculate internal pressure generated in an enclosure
2. how to calculate energy released during test and how to co-relate it with pressure generated.

Kalpesh

 

[dpc]

Circuit breaker short circuit ratings are based on testing using external bolted (zero impedance) faults. With a bolted fault, there is no arcing at the fault point, so not much pressure increase.

Maybe you could explain what you need to calculate this for?

 

[itsmoked]

I believe they use only about 1 Volt to test the breakers. And, that test only goes up to the specified interruption current not the available source current.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[KRC83]

Test has been conducted on enclosure along with breakers.
Breaker are rated for 240vAc 200A 22kA
Enclosure is rated for 3R.
Short circuit test is conducted for 22KA for 0.1 sec. Arc generated in breaker compartment… breaker tripped but still arc generated inside breaker compartment.
Covers flew away at short circuit test.
Test was just like internal arc test.

 

[LionelHutz]

As you have seen, pressure is related to what arcs inside during the test.

What you need to do now is evaluate the enclosure contents and determine if the components would have passed if the cover had not blown off. If they would have passed, you fasten the cover better. If they would have failed, you fix what failed and try again.

 

[cranky108]

I was thinking the test was with 6 feet of rated wire, not bolted.
Maybe things have changed in the last 30+ years.

 

[KRC83]

yeah.. so to fasten the covers and ensure that next time it does not fail.. do we have any calculations, that by passing the short circuit current of 22kA through breaker, energy released can be calculated and based on energy, pressure can be calculated.

 

[dpc]

You're talking about two completely different scenarios. The short circuit rating of the breaker has nothing to do with the arc-rating of an enclosure.

 

[che12345]

Dear Mr. KRC83 (Electrical)
"...When Low Voltage MCCB say 200A 22kA 240AC is tested for short circuit test can anyone provide below information
1. How to calculate internal pressure generated in an enclosure
2. how to calculate energy released during test and how to co-relate it with pressure generated..."
Che. 1. Following are the main standards : In the IEC world IEC 60947-1,2 ; in the US world ANSI C37.50. The test requirements differs.
2. IEC 60947-2 sub-clause 8.3.2.1 states.......
a) Circuit breaker shall be tested in free air,
b) ... if a CB may be used in specified individual enclosure and has been tested in free air, it shall be additionally tested in the smallest of such enclosure... where the details including the dimension of the enclosure, shall be stated in the test report...
3. Arrangement of the short-circuit opening/closing test, the bolted shorting is NOT on the [CB load terminals] but some distance away. There is NO arc at all at the bolted shorting point. On the other hand, heavy arc across the CB during closing/opening on a short-circuit test. On various short-circuit tests conducted in England, Australia and Sweden that I witnessed, the lab does NOT record the [over-pressure] on an open air test.
4. However, the [over pressure] is of great importance under a different standard e.g. IEC 61439-1,2 etc., where the criterial are listed.
Che Kuan Yau (Singapore)