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Confused with power calculation

Discussion in Server Room & Data Center Design Best Practices started by Giji , 8/13/2011 8:12 PM
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Confused with power calculation

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  • giji_george

    I am planning for 16 racks data center with 10KW each rack (single phase load). So total load would be (10KW x 16) 160KW 1ph.

    So based on my logic when I choose a UPS with *3ph output*, I can divide it by three. That means a UPS with 54KW 3ph should be sufficient. (plus buffer, I would think of SY96K96H-PD)

    But I was told that I cannot divide load by three and must use UPS rated 160W 3ph or higher.

    Can anyone advise what should be the correct method?

    Thank You

  • TheFran

    If you have 160kW load then you need a UPS rated for 160kW (around 200kVA) regardless of whether it is single or three phase.

    The difference is that with a 160kW single phase system you would have a total current of around 840Amps on 1 phase. Whilst with a three phase arrangement the current would be 280Amps per phase.

    Note: the above is based on the voltage in my region which is 240V single phase and 415V three phase - if you're in the US you will need to calculate based on yoru local voltage.

    Hope this helps.

  • upsguy

    A few things to note about your calculations..

    1) Most three phase systems have a output PF of .9 or 1.0 so 160KW/177KW or 160KW/160KVA at PF 1.0
    2) On a three phase UPS the current load on 160KW is about 222amps at 415v at PF 1.0 or 192amps at 480v PF 1.0

    I do not believe APC makes a single phase UPS at 160KW so a three phase unit is really your only option.

    SY200K250DR-PD This UPS is a 200KW expandable to 250KW and can work with many different voltage inputs. You would have 175KW of power modules with 1 extra power module in reserve to keep your system online in case of a failure. 200KW total if your do not require a reserve module. Or you can have 175kw of modules no reserve.

  • giji_george

    Thank you all for the valuable input.

    To confirm, when APC say 10KVA 3 Phase UPS, does it means 10KVA in each phase or 10KVA in total (appox 3.3KVA per phase)?


  • upsguy

    Yes a 10kva 3 phase UPS is rated by its total capacity which is the sum of all 3 phases. So 10KVA 3 Phase UPS = ~3.3kva per phase.

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