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PFC for multiple small fan motors?


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#1 cismontguy

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Posted 29 October 2003 - 04:38 PM

Hello and thank you for reading my posting. This is a wonderful web site! I am new to AC/DC motor controls and taking night course in the field right now to learn more.

I have a current project in my shop that is presenting a problem/concern. I have a bank of 56 (8 rows of 7 fans each) 120V, 60 Hzt, .2 A axial flow fans. (computer cooling fans 4-1/2" sq.) Each is individually wired to a terminal strip with 120V 15A coming in.

When I place my clamp on Amp meter I get a reading of like 21A @ start up and 13A at operation. This seems excessively high? My professor says it is due to my need of a Power Factor Correction capacitor(s)?

So is it possible for a novice to determine the correct PFC cap? I saw a program you can download? Any ideas and or constructive suggestions would be greatly appreciated!

CismontGuy

#2 marke

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Posted 29 October 2003 - 06:14 PM

Hello cismontguy

Yes, if you correct he power factor, you will draw less current.
You will not necessarily see much impact on the start current though.

To determine the amount of power factor correction required, you need to determine the existing power factor or KW consumed. Once you have this figure, then you can easily calculate the pf required.

Best regards,

#3 cismontguy

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Posted 30 October 2003 - 01:45 PM

Mark: thanks for your reply. Is there some way for me measuring the existing power factor? I mean I do not know how to determine this number so I can then try and calculate the size of capacitor(s) I would need to use? The fans are built by Commonwealth Ltd Corp in Taiwan but I cannot find a web site or some kind of contact information for them? I bought the fans from Jameco, here in the USA.

Cismontguy

#4 marke

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Posted 30 October 2003 - 06:15 PM

Hello cismontguy

To determin power factor, you can use a power factor meter or transducer, or you can measure the power consumption and current draw and caluclate the power factor from kw/kva, or you can measure the angle between the voltage and the current using an oscilloscope and calculate the power factor as Cos phi.

Best regards,




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