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Alternator size v.s. rpm rule of thumb
2

Alternator size v.s. rpm rule of thumb

Alternator size v.s. rpm rule of thumb

(OP)
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?

RE: Alternator size v.s. rpm rule of thumb

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

RE: Alternator size v.s. rpm rule of thumb

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

RE: Alternator size v.s. rpm rule of thumb

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

RE: Alternator size v.s. rpm rule of thumb

Sorry, it should be 10^5.

RE: Alternator size v.s. rpm rule of thumb

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

RE: Alternator size v.s. rpm rule of thumb

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.

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