Re: Generator Ratings (back to basics)

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Spir Georges GHALI

Dear Mr. Mill ;


Refer to this topic, I would mention to the following points :

– In the table and all equations you mention only to the “ small Single Phase Generators ”, where are the 3 Phases Generators ?

– The table mentioned to the small powers of Single Phase Generators and the relevant Loads in Watts, but those loads’ values are theoretical, because :

  • Most of actual loads aren’t 100% resistive, that means the PF is smaller than 1 ( exp. if we have a load “ P : 800W, PF : 0.70 ”, that means the minimum apparent power that we need is “ Smin : 800/0.70 = 1140VA ”, so, 1kVA generator can’t afford this load of 800W ).
  • Normally, the name plate of any generator mention to a “ PF value ”, and that value guides us to know to the maximum active power “ P : W  or  kW ” can be consumed of it. Noting that you mentioned to this point in “ Standby Power Rating ” paragraph.

– I think we should also mention that the maximum loads of any Standby Generator should not exceed “ 80  to  85% ” of its Rated Apparent Power “ S : kVA ”.

– It’s mentioned in “ Prim Power Rating ” paragraph that for this type a 10% of the rated apparent power is allowed as an Overload only one time each 12 hours, but it’s not mentioned the duration of this allowed overload ???