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Old 12th January 2006, 10:28 PM   #1
Tweeker is offline Tweeker  United States
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Default Choke input 3 phase rectification voltage?

If I were to use a 6 pulse bridge rectifier with a choke input LC filter, relative to the AC RMS voltage across each secondary, what DC voltage out would I get:

With delta connected secondaries?
With wye connected secondaries?
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Old 12th January 2006, 10:36 PM   #2
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Tweeker,

The ralationship between delta and wye is the square root of 3 (1.73). So if you measure 120 volts from leg to neutral (wye); you will measure 208 volts from leg to leg (delta... or wye for that matter).
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Old 13th January 2006, 01:19 AM   #3
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I know 3 phase wye bridge rectified without a choke but capacitor gives 2.45*VAC RMS= VDC, what does it give with a choke? 1.73*.9= 1.56?

With delta connected secondaries, does this mean output with choke would be VAC RMS * .9 = VDC?

What scant information I can find seems to indicate this isnt quite right, choke input polyphase rectifiers seem to be obsolete.
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Old 13th January 2006, 02:13 AM   #4
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I will have to look... in a little red book I have...

Wait for tomorrow... I can't promise an answer... I just don't want to give you a BS one.

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Old 13th January 2006, 05:21 AM   #5
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In fact Im pretty sure it isnt * .9, average voltage would be much higher than with single phase.
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Old 13th January 2006, 05:08 PM   #6
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hey Tweeker,

The average voltage factor is 0.954969. I couldn't find my little red book so I Armstrong-ed it in Excel... PM me if you want the spreadsheet.

Remeber, when you sum the 3 rectified phases the voltages don't add... they merely overlap... only the biggest voltage wins...

OH... this isn't RMS... multply by 1.414


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