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Thread: Generator Rating Question

  1. #1
    Join Date
    Jul 2012
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    Generator Rating Question

    Why the bigger generators are rated in kW instead of KVA rating. E.g i have seen 2500kW rating for both gas gensets and diesel gensets.

    If some one can explain please..

    Thanks

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    If you don't know, ask those who knows

  2. #2
    Join Date
    Dec 2011
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    Ocala, Florida, USA
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    Quote Originally Posted by Sajid khan View Post
    Why the bigger generators are rated in kW instead of KVA rating. E.g i have seen 2500kW rating for both gas gensets and diesel gensets.

    If some one can explain please..

    Thanks

    Sent from my GT-I9300I using Tapatalk

    Most generators I have seen large and small are rated in both KVA and KW.


    I know what I don't know, and I know where to go to find it!

  3. #3
    Join Date
    Feb 2003
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    New York, 40.7514,-73.9925
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    All generators are rated in both kW and kVA.

    Sometimes depending on the load, one will be more of a critical threshold than the other. Whichever you hit first is the limit.
    Ron

  4. #4
    Join Date
    Nov 2010
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    Fort Collins, Colorado
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    Quote Originally Posted by Sajid khan View Post
    Why the bigger generators are rated in kW instead of KVA rating. E.g i have seen 2500kW rating for both gas gensets and diesel gensets.

    If some one can explain please..

    Thanks

    Sent from my GT-I9300I using Tapatalk
    As already mentioned, the genset will have both a KW and KVA rating. The KVA rating will tell you how much current it can handle. The KW rating tells you how much power it will deliver. With a genset this is critical info as the KVA relates to the generator current capacity and the prime mover relates to the power it can deliver (KW). As an extreme example, a genset rated 100 KVA @ .5 PF will only have enough engine to provide 50 KW.

  5. #5
    Join Date
    May 2008
    Location
    West Chester, PA
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    555
    I like to think of it like this; kW is the rating of the engine, kVA is the rating of the alternator.

    Because the kW rating is typically 80% of the kVA, it means the engine can't produce enough energy to overload the alternator as long as the load power factor is above 80%.
    Alternate current
    Line to ground and ground to line
    Current alternates

  6. #6
    Join Date
    Jun 2017
    Location
    WI, USA
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    363
    Standard application is based on 0.8 PF. If the actual PF is higher, you may get more out of the generator, which is why you must size this way. We don’t typically design beyond the rating for capacity...so using kW. This also helps concerns for elevation derates if they apply as conservative.

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