30-Cycle ATS Rating

[philly]

I'm trying to get a better understanding of an ATS 30-cycle rating. Does this rating only apply to ATS's that have integral power circuit breakers to them or does this rating also apply contactor based or molded case breaker based ATS?

I'm looking at a situation where an ATS if fed from an upstream power circuit breaker that does not have an Instantaneous setting and only has long time and short time settings. The ATS is a 400A ATS with molded case breakers. Should this ATS have a 30-cycle rating in order to be adequately protected by upstream breaker or do only certain types of ATS (with integral power breakers) have a 30-cycle rating.

I know ATS have "specific breaker", and "any breaker" ratings and I have also seen "30 cycle rating" but now sure how this is applied.

 

[ron]

If you are feeding downstream equipment (in this case an ATS) from a power breaker without instantaneous protection, you need to be sure the downstream equipment is 30 cycle rated.

Russelectric and ASCO (contactor based) make 30 cycle rated ATS products.

Why not turn inst on for the upstream power breaker and not worry about the 3 or 30 cycle rating for the ATS?

 

[philly]

If you are feeding downstream equipment (in this case an ATS) from a power breaker without instantaneous protection, you need to be sure the downstream equipment is 30 cycle rated.

Russelectric and ASCO (contactor based) make 30 cycle rated ATS products.

Why not turn inst on for the upstream power breaker and not worry about the 3 or 30 cycle rating for the ATS?

The issue is that the trip unit on the upstream power breaker is an LS breaker only and does not have an Instantsnrous setting or an Instantsneous override.

Is the 3 cycle rating the same as the "any breaker" rating as long as the breaker has an Instantaneous?

 

[ron]

Yes, "any breaker" typically means it has instantaneous protection and will clear a fault in 3 cycles or less.

 

[philly]

If you are feeding downstream equipment (in this case an ATS) from a power breaker without instantaneous protection, you need to be sure the downstream equipment is 30 cycle rated.

Russelectric and ASCO (contactor based) make 30 cycle rated ATS products.

Why not turn inst on for the upstream power breaker and not worry about the 3 or 30 cycle rating for the ATS?

Do all ATS's have a 30-cycle rating or only particular ones have a 30-cycle rating. I cannot find a 30-cycle rating for a particular Eaton ATS (molded case breakers in ATS) so I'm not sure if that means the rating doesn't exist or I need to dig deeper?

If the 30-cycle rating does not exist then I'm assuming that the upstream breaker must have Instantaneous protection? What if the upstream breaker does not have INST protection but the breakers in the ATS have it?

Do all ATS have both a 3-cycle rating and a "specific listed" rating when used with specific breakers? I see the specific breaker rating listed for some ATS but don't see that listed for others.

 

[ron]

Do all ATS's have a 30-cycle rating or only particular ones have a 30-cycle rating. I cannot find a 30-cycle rating for a particular Eaton ATS (molded case breakers in ATS) so I'm not sure if that means the rating doesn't exist or I need to dig deeper?

No, it is a marketing aspect started by Russelectric and taken on by ASCO, Others may have it, but breaker ATS's likely do not because they are using molded case or insulated case breakers.

 

[texie]

I'm trying to get a better understanding of an ATS 30-cycle rating. Does this rating only apply to ATS's that have integral power circuit breakers to them or does this rating also apply contactor based or molded case breaker based ATS?

I'm looking at a situation where an ATS if fed from an upstream power circuit breaker that does not have an Instantaneous setting and only has long time and short time settings. The ATS is a 400A ATS with molded case breakers. Should this ATS have a 30-cycle rating in order to be adequately protected by upstream breaker or do only certain types of ATS (with integral power breakers) have a 30-cycle rating.

I know ATS have "specific breaker", and "any breaker" ratings and I have also seen "30 cycle rating" but now sure how this is applied.

Here is a Cummins technical paper on 30 cycle T-switches that may be of interest: http://power.cummins.com/sites/defa...echnicalpapers/PT-9005-30-CycleDangers-en.pdf

 

[Mike01]

Transfer Switch Ratings

Transfer Switch Ratings

UL-1008 is the standard when it comes to transfer Switch Equipment ratings, and was recently updated. The terminology 30-cycle has been revised transfer switches are referred to now on a time based 0.05 sec [3-cycle] and what they refer to as short time ratings, however short time ratings can range from 0.05 – 0.5sec depending on the manufacturer and how they tested their switches. Some manufacturers will list multiple short time ratings based on the different “times” for example one manufacturer will list a switch with a 0.05[3-cycle rating] in addition to multiple short time ratings. [ex 0.1, 0.15 up to and including 0.5sec – 30 cycles]. The any breaker ratings are based on a specific time depending on the switch ampacity and requires a circuit breaker with an instantaneous trip response. When tested with specific breakers you may be able to get some additional kA. Most manufactures can provide contactor based short time rated switches you just have to consult with them first. If the switch is a breaker based switch it will likely require a breaker with instantaneous ahead of it if the transfer switch is using MCCB, or even ICCB as these are three cycle type breakers. The one item to watch is that in the UL standard when using the any breaker ratings. The overcurrent protective device “must include an instantaneous trip response and shall include a short time trip response”. If a breaker with an adjustable short time feature is used it may require the use of a short time rated switch. I do not necessarily agree with this however some manufacturers are enforcing this. See the image attached image this is from one manufacturer’s literature on their UL equipment label.