Square D powerpact breaker ratings?

[mbrooke]

Im having some difficulty understanding this breakers interrupting rating. Under Icu and Ics to the right 2 different ratings appear. My question is what do situation are they refering to or what do they stand for?

 

[Smart $]

Im having some difficulty understanding this breakers interrupting rating. Under Icu and Ics to the right 2 different ratings appear. My question is what do situation are they refering to or what do they stand for?

My guess is ratings under IEC or the other standards listed at right.

 

[jim dungar]

That breaker has both UL and IEC ratings.

The left hand side shows that UL and CSA list it as 25kA @240VAC.
The right hand side shows the ratings if the breaker was being compared to a short circuit study using IEC criteria. These rating are ignored if you are applying the breaker in North America.

 

[Jraef]

If you are applying the breaker in an IEC country, then the difference between Icu and Ics is that they recognize two different performance criteria for breakers. The Icu rating is the maximum interrupt it can handle at that voltage, but the breaker is NOT expected to be used again after interrupting. In other words it is allowed to sacrifice itself in the performance of it's duty, kind of like an expensive 3 pole fuse. In North America that is not done, the IC rating has only one test criteria level.

The Ics rating means that the breaker must clear that level of fault, then reset and be useful again. That is the equivalent to the UL test.

 

[mbrooke]

If you are applying the breaker in an IEC country, then the difference between Icu and Ics is that they recognize two different performance criteria for breakers. The Icu rating is the maximum interrupt it can handle at that voltage, but the breaker is NOT expected to be used again after interrupting. In other words it is allowed to sacrifice itself in the performance of it's duty, kind of like an expensive 3 pole fuse. In North America that is not done, the IC rating has only one test criteria level.

The Ics rating means that the breaker must clear that level of fault, then reset and be useful again. That is the equivalent to the UL test.

Thank YOU! I would have never thought of that. Its now understandable. As for the UL, its based on a 3 strikes rule, ie if the breaker is subjected to 3 faults (or how ever many it is) at rated voltage at 25ka, then after the 3rd strike the breaker should be changed?


As for the rated voltage of 240, how is that applied relative to the UL AIC? Are the poles rated to interrupt 120 volts or are they designed to interrupt 240 volts in the event the system is say corner grounded?

 

[jim dungar]

Thank YOU! I would have never thought of that. Its now understandable. As for the UL, its based on a 3 strikes rule, ie if the breaker is subjected to 3 faults (or how ever many it is) at rated voltage at 25ka, then after the 3rd strike the breaker should be changed?

Actually the UL489 test is: Open-Close-Open at 100% of its AIC rating.

As for the rated voltage of 240, how is that applied relative to the UL AIC? Are the poles rated to interrupt 120 volts or are they designed to interrupt 240 volts in the event the system is say corner grounded?

If the ratings depend on the L-G voltage it will be noted on the label, otherwise they are L-L. Corner-Grounded systems require special testing and their AIC ratings are almost never on the standard label.

Also, do not try to compare the IEC values against UL ones. The criteria and methodology for determining the testing fault currents are substantially different.

 

[mbrooke]

Actually the UL489 test is: Open-Close-Open at 100% of its AIC rating.


If the ratings depend on the L-G voltage it will be noted on the label, otherwise they are L-L. Corner-Grounded systems require special testing and their AIC ratings are almost never on the standard label.

Also, do not try to compare the IEC values against UL ones. The criteria and methodology for determining the testing fault currents are substantially different.

Ok got it. So the poles are based on an UL AIC of 240 vac rather than 120?

 

[jim dungar]

Ok got it. So the poles are based on an UL AIC of 240 vac rather than 120?

The UL testing involves L-L and L-G faults. The labeling just shows the L-L case which corresponds to the industry practice of only 'posting' L-L bolted fault currents for multi-pole devices. L-G faults are usually considered during actual "device evaluation' studies.