LOAD of EDG 1

[zaza123]

"The rating of the Emergency generator should be greater than the sum of all the connected loads."
just need to confirm this as i believe it should be.
for eg if your connected load is 1000KW , so generator should be atleaast 1000KW

 

[itsmoked]

That is insanely rudimentary. That kind of logic would likely fail you. <dramatically>

Keith Cress
kcress -

http://www.flaminsystems.com

 

[zaza123]

dear Keith please explain,

What i know is that the generator rating is normally in KVA.As per the power factor the load it can supply can be deducted.

 

[waross]

"The rating of the Emergency generator should be greater than the sum of all the connected loads."

Who can argue with that!!
Except where the demand factor is so low that you have underloading issues.
And of course when part of your connected load is a large motor and the generator stalls or trips out on undervoltage.
Was your statement written by an MBA?

What i know is that the generator rating is normally in KVA.As per the power factor the load it can supply can be deducted.

You must not exceed either the kW rating or the KVA rating.
Search this site for discussions of generator loading.
Search manufacturers sites for generator sizing software.
Try Olympian, or Marathon (Cat).
Try Onan.
Hire an expert.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

To continue. For example, it's not just about the steady state loads it's also about the types of loads. Certain loads need much larger generator capacity just for starting.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[burnt2x]

Simply put; you need to factor in the starting current expected to be drawn by motors connected to this emergency circuit in sizing your generator.

 

[VTer]

Not just motors but any equipment on the unit that has any inrush current needs to be factored with respect to skVA, skW, permitted voltage/frequency dip . For this reason most large loads are divided into different load scenarios to avoid over-sizing gen sets by placing time delay relays and starting these loads separately and not all instantaneously. Another things to point out (the way I look at it) is that the engine produces the usable power (watts) and the alternator will produce your VARS to give you your total KVA on the output of the generator. Simply adding running kW and kVA is not recommended, nor good practice when sizing gen sets. Most people use some kind of software to correctly size the unit. Look into Electric Power SpecSizer from

http://www.cat.com/cda/layout/cda/layout?m=37508&x=7&f=111183

"Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic — and this we know it is, for certain — then it is a mere question of time when men will succeed in attaching their machinery to the very wheelwork of nature". – Nikola Tesla

 

[marks1080]

"Was your statement written by an MBA?"


That statement is very funny... and unfortunatly in a lot of cases is probably very true.

 

[zaza123]

hello !
no my statement wasnot written by MBA, it was a thought captured by words!
well i need to connect more load on my EDG system thats why this particular question was raised.one more thought that iam having is when the normal supply incomer trips & the EDG starts , what happens to the critical loads during that moment. i know the real situation will depend on the design of that perticular scheme.I hope motors having underload will trip, those having hold on contactor & re acceleration scheme will come back to line after some seconds.

 

[waross]

The action of equipment during a short power outage (stay connected or disconnect) will depend on the control scheme of the individual equipment.
When the science of calculating the maximum load allowable on a generator indicates that no further loading is allowed, the art of loading a generator may still allow some load to be safely added.
Critical loads may be fed from an Uninteruptible Power Supply.
In this case the load to be considered is the UPS itself, with little regard to the loads connected to the UPS.
Although your question may be stated in a few words, an accurate answer can not be so simply stated.
The "Science" of generator loading may indicate the need of a larger generator.
The "Art" of generator loading may enable you to continue with the original generator.
Considering the cost of purchasing and installing a larger generator, it is well worth the time and effort to find someone familiar with the Art of generator loading and paying him a few thousand dollars to share his knowledge with you.
This is not sarcasm or a put down. This is sincere advice from someone who has many times had to tune up installations where the generators were undersized.
Bear in mind that generator sizing may range from less than 50% of the connected load to 250% or more of the connected load.

Bill
--------------------
"Why not the best?"
Jimmy Carter