from the electrical department...
Generator selection
Engineering and workplace issues. topic
Posted by Generator on 4 March, 2013 - 2:10 am
Dear sir,

we have air flow and one FRP fan is fitted in that air flow. which fan rotate on app. 1000 rpm. so, can I use this air flow rpm for generating single phase 230 volt 50 hz. supply? If yes, then suggest suitable capacity alternator. and how much load can be run on the alternator?

thank you.

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Posted by Phil Corso on 4 March, 2013 - 10:09 am
Generator… following is a procedure you can follow:

1) Determine the area, A, swept out by the fan blades
A = pi x (D^2)/4), where D =blade diameter

2) Determine the air velocity, V, of the air flowing through Area A!
I'll leave that up to you!

3) Determine the mass, M, of the air flowing through Area A:
M = rho x A x V, where rho = air density.

4) Determine the energy, E, of the air flowing through Area A:
E = (1/2) x Ma x V^2 = (1/2) x rho x A x V x V^2 = (1/2) x rho x A x V^3

5) Determine the power, P, produced by the air flow.
P equals the change in Energy with respect to time, but it requires knowledge of differential equations (available on request), the end result is P = (1/2) x rho x A x V^3

The conclusion normally reached is, "There is a lot of energy/power in wind!" Unfortunately, in 1919, Albert Betz, a German physicist, determined the theoretical value is unreachable! He proved the maximum available power is only 59% of that derived above!

Thus the practical wind-mill will produce only:
P = (1/2) x Nb x Nm x Ne x A x V^3, where Nb is the Betz Factor, and Nm and Ne are the efficiencies of the turbine and generator, respectively!

Regards, Phil Corso

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Posted by Phil Corso on 4 March, 2013 - 11:04 am

I forgot to mention viirtually all wind-power applications have a Betz factor well below 0.59!


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Posted by CSA on 5 March, 2013 - 12:36 am
There's also the minor matter of speed of the Fiber Reinforced Plastic fan vs frequency. A 6-pole machine would be required for 1000 RPM @ 50 Hz.

But there are a LOT of other factors to be considered as well.

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