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-   -   Choke input 3 phase rectification voltage? (http://www.diyaudio.com/forums/power-supplies/71623-choke-input-3-phase-rectification-voltage.html)

 Tweeker 12th January 2006 10:28 PM

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?

 poobah 12th January 2006 10:36 PM

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).

 Tweeker 13th January 2006 01:19 AM

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.

 poobah 13th January 2006 02:13 AM

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.

:xeye: :D

 Tweeker 13th January 2006 05:21 AM

In fact Im pretty sure it isnt * .9, average voltage would be much higher than with single phase.

 poobah 13th January 2006 05:08 PM

2 Attachment(s)
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

:D

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