Generator Sizing

[adamscb]

Forum,

We have a 300hp motor we're trying to get up and running using a generator. What size of generator should be rent?

I say we should get a 300kW, because 300hp ~ 225kW, then add another 75kW for the inrush. Thoughts?

 

[Ingenieur]

Forum,

We have a 300hp motor we're trying to get up and running using a generator. What size of generator should be rent?

I say we should get a 300kW, because 300hp ~ 225kW, then add another 75kW for the inrush. Thoughts?

starting method?
you need to determine the motors starting kva
then find a generator, more precisely alternator, that can supply it
in my limited experience the gen is usually twice the motor load size

 

[adamscb]

Planning on starting it across the line. I'll look up the code for kVA/hp and calculate the starting kVA

 

[eric9822]

Inrush current is usually about 6-10 times motor FLC. I think a 75KW allowance is low.

 

[GoldDigger]

Inrush current is usually about 6-10 times motor FLC. I think a 75KW allowance is low.

Except that if the generator voltage simply sags under heavy load instead of collapsing you have, in effect, reduced voltage starting for the motor That reduces the load requirement on the generator.

 

[Ingenieur]

Say 1700 kva starting 30% V droop to start motor

typical 300 kw
1000 starting kva at 35% http://www.kohlerpower.com/onlinecatalog/pdf/g5352.pdf

Typical 400-500 kw
1800 starting kva at 35% http://www.kohlerpower.com/onlinecatalog/pdf/g5355.pdf

note for a given engine the alternator has various starting kva ratings

 

[Sahib]

One cost effective way is look for a rental supplier who can supply a generator coupled to an engine of lower size. The point is engine size need not be as big as the alternator coupled to it and this would be economical for you to operate.