so, i'm taking up a course on electrical machine design and our professor gave us the equations for computing the different values required for a given specification.(adsbygoogle = window.adsbygoogle || []).push({});

here is my problem:

given these two equations:

laD^2 = (W/N)(6.079x10^8)/(Byqr) --> eq. 1

and

la = pi(D)(r)/(pK) --> eq. 2

where la = length of armature core (inches)

D = diameter of armature core (inches)

r = ratio of pole arc to pole face

By = air gap density

W = output of armature (watts)

N = speed

p = number of poles

K = some constant ranging from 0.667 to 1

equation 1 came from

W = Z*Ec*Ic

where Z = total number of armature conductors

Ec and Ic = voltage and current on the conductor

Ec = 6.45(Bg)(la)(pi)(D)(r)(N)/60x10^8

where Bg = average flux density in the air gap under each pole (gauss)

and

Ic = q(pi)(D)/Z

where q = specific loading

substituting all Ec and Ic in W you can get equation 1.

and then you can solve for D by combining the two equations.

my question is where does the second equation came from??

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# Armature Diameter formula question

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