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Thread: Emergency Diesel Generator Calculation

  1. #11
    Join Date
    Nov 2007
    Posts
    867
    Quote Originally Posted by i.engrqasim View Post
    It is an industrial setup (a waste water (sewage) pump station).
    There is no voltage dip specified in the generator specifications, the 3% is specified voltage drop for cables, which the contractor has used.
    The contractor has done calculation for a 1250 KVA. However we have a 1520KVA Generator with 1770 KVA alternator.
    Voltage dip shall be in a range that may not harm the VFD's.
    Please see the difference of the "voltage drop" compared to "voltage dip". Those are not the same animal. Voltage dip is very important as some equipment don't play well when the supply voltage suddenly dips during starting of big motor loads.

  2. #12
    Join Date
    May 2018
    Location
    Saudi Arabia
    Posts
    11
    Quote Originally Posted by topgone View Post
    Please see the difference of the "voltage drop" compared to "voltage dip". Those are not the same animal. Voltage dip is very important as some equipment don't play well when the supply voltage suddenly dips during starting of big motor loads.
    We don't have large direct on line motors. It's an 8 hour emergency operation. our large motors are run by VFD's, so no voltage dip problem there.
    I've read an allowed voltage dip of 30% for industrial loads, however with 1520KVA enginer and 1770 KVA alternator, I highly doubt we'll reach even 20%.

    The caterpillar analysis is done for 1250 KVA and that is probably the reason for the shown 26% v dip.

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