Max.HP on Generator 1

[lishaji]

I was wondering whether there is a formula to calculate the maximum motor rating in hp that can be started on available Generator kVA.
Any input would be much appreciated

 

[itsmoked]

Not really..

As motors can be all over the place on their starting demands. Much more needs to be understood to make the assessment.

What kind of motor
What load it is driving
What starting system you desire - can afford.
Voltage drop allowed
etc
etc

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[waross]

A quick rule of thumb.
If the generator rated current is twice the motor rated current it may or may not start.
If the generator current is 2.5 times the motor rated current it will probably start but expect a severe voltage drop and possibly some frequency droop (which will make the voltage drop worse).
If the generator is rated at three times the motor rated current the performance is usually acceptable in all but extreme cases.
There are formulas and models, but they want the kind of input that itsmoked mentioned, and the factors he mentioned apply to these rules of thumb.
Try the major manufaturers web sites for sizing information.
Onan,
Cat,
F.G. Wilson, (Now owned by CAT)
John Deere used to publish a lot of generator data under their OEM group.
respectfully

 

[lishaji]

I came across a formula:-

Maximum Horsepower Availabe for Starting = (Motor.Start.Factor x Gen.kVA x % Avail.Gen.kVA) /(100 x Motor.kVA.per.Hp_Locked_Rotor)

But I don't know what is Motor.Start.Factor?
Eg. If a 600 kva generator is used with an intial load of 160kva assuming a 25% voltage dip, the maximum horsepower would be

= 1 x 600 x 75/(100 x 505) = 82 hp

 

[rbulsara]

See faq237-766