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Forum Index : Electronics : Electrical Math, Argh!

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gaspo
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Joined: 25/06/2018
Location: Australia
Posts: 61
Posted: 07:05am 15 Aug 2019
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  Ironmaiden said  
14/ (3.142 x 2.0 x 60 x 230)
I get 1.614406037e-4


The other way to interpret scientific numbers is to prepend as many zeros in front of the number as the exponent indicates and then move the decimal point to be after the first zero.

1.61440e-4 = 0000161440 = 0.000161440, this is in Farad.

You can then group digits after the zero into three to get milli, micro, nano, pico.
0.000 161 440 = 161.44uF
Edited 2019-08-15 17:06 by gaspo
 
Ironmaiden
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Joined: 09/07/2019
Location: United States
Posts: 53
Posted: 03:05pm 15 Aug 2019
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Poida, Gaspo. A big thank you to both of you gentlemen.

Honestly, We never covered scientific notation in high school. But then our education system these days are complete rubbish. I graduated in 2010 so am a victim of the indoctrination campuses that don't actually teach a thing except political agendas.

Robert
Edited 2019-08-16 01:12 by Ironmaiden
 
Ironmaiden
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Joined: 09/07/2019
Location: United States
Posts: 53
Posted: 04:26pm 15 Aug 2019
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Going on the data of page 38, I am getting a number greater for the delta connected capacitor bank.

That can't be right though because a star connected capacitor bank requires up to 3 times the uf of a

delta connected capacitor bank.

3 x 230 x 14= 9660VA

Hence, Real power,

9660 x 0.87 = 8404W

The reactive power can be obtained from the power triangle.

(9660^2-8404^2) = 2268VAR

Hence, The reactive power per phase,

2268/3 = 756VAR

For delta connected capacitors,

V phase = V line

I phase = Q phase/ V phase = 756/230= 3.28A

From equation 6, C = 3.28/(2pi x 60 x 230)=378uf

378uf being the total amount of capacitance needed means each of the three capacitors would need to be 126uf. That seems like a crazy amount for a 4KW induction generator. Surely that much UF would blow the windings out in a couple minutes.

I've excited this generator with 3 50uf 440vac capacitors, as does most of the youtube videos on machines of 5.5kw up to 15kw.

I'm thinking page 38 and 36 are reversed? Surely the 378uf is what would be needed for a star connected capacitor bank. The 161uf for a delta connected capacitor bank. Have I found a fatal flaw in Nigel's book???

Robert
Edited 2019-08-16 02:48 by Ironmaiden
 
Ironmaiden
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Joined: 09/07/2019
Location: United States
Posts: 53
Posted: 12:35am 16 Aug 2019
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While doing some research this evening I have come across an older book on induction generators written by Skat, A Swiss engineering firm in conjunction with German GATE a division of GTZ Gmbh. http://skat.ch/book/manual-on-induction-motors-used-as-generators-volume-10/

Robert
Edited 2019-08-16 10:36 by Ironmaiden
 
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