Alternator size v.s. rpm rule of thumb 2

[lengould]

I've heard but lost track of a rule of thumb relating the ratio of stator size (?mass?) of an AC generator to the rpm of the rotor. Has anyone else come across this? If so, do you know if the rule relates only to iron or to windings etc total?

 

[edison123]

output of an electrical machine is proportional to its volume and speed. Could this be what you are looking for ?

 

[DougMSOE]

I think that you are describing what is known as the output factor.

Of=(kva*10^50)/(RPM*D*l^2)

D=stator inside diameter (if I remember correctly in inches)
l=gross core length (if I remember correctly in inches)

Handbook of Electrical Engineers 10th edition

 

[jbartos]

Suggestion to the previous posting: Please, would you clarify 10^50 in your equation?

 

[jbartos]

Suggestion: Please, notice that the Output Factor is also linked to Load Factor. Visit

http://www.energy.qld.gov.au/electricity/infosite/glossary/glossaryofterms.htm

for more info

 

[DougMSOE]

Sorry, it should be 10^5.

 

[jbartos]

Suggestion: Reference:
Donal G. Fink, John M. Carroll "Standard Handbook for Electrical Engineers, 10th Edition, McGraw-Hill Book Company, 1968,
page 6-5
equation 6-2
Output Factor = (kVA x 10**5)/(RPM x D**2 x L)
where
D is armature inside diameter
L is gross core length

 

[jbartos]

Suggestion/Correction
Donal should read Donald
Additionally, Equation 6-2 can be elaborated to Equation 6-3 as:
Output Factor= (Bgf x kac/in)/8600
where:
Bgf is peak of fundamental component of air-gap flux density in lines per square inch
kac/in is rms effective armature kiloampere conductors per inch of armature periphery at inside diameter D.