Three phase full wave bridge rectifier - Electronic Circuits Projects Diagrams Free

cj62565 · 9th November 2009, 11:40 PM

Hi,
I was asked in school, if I have 480vac going in and 630vdc coming out, how would I come up with this dc figure. I was not given any other values, and I'm comoing up with around 678vdc. There would be some voltage drop associated with the diodes but that is minimal. Around 4.2v. So I know thats not the reason for the drop of around 48v. This is not a test or homework, but just something my instructor asked at the end of class.

CJ

RCinFLA · 10th November 2009, 03:12 AM

Are we talking about r.m.s. effective D.C. ? There is ripple associated with three phase full wave rectified D.C. The rms D.C. would not equal peak value of AC unless there is a filter cap on output to keep the peak.

Sceadwian · 11th November 2009, 02:26 AM

Doesn't this have something to do with the phase angle difference from each leg?

RCinFLA · 12th November 2009, 11:38 PM

Okay, you forced me to do the calculation.

Ignoring rectified voltage drop.

480 vac rms three phase full wave rectified

Peak = 678.82 vdc.

Minimum = 587.88 vdc

Ripple = 90.94 vpk-pk

D.C. rms = 648.62 vdc.

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9th November 2009, 11:40 PM	#1
cj62565	Three phase full wave bridge rectifier Hi, I was asked in school, if I have 480vac going in and 630vdc coming out, how would I come up with this dc figure. I was not given any other values, and I'm comoing up with around 678vdc. There would be some voltage drop associated with the diodes but that is minimal. Around 4.2v. So I know thats not the reason for the drop of around 48v. This is not a test or homework, but just something my instructor asked at the end of class. CJ

10th November 2009, 03:12 AM	#2
RCinFLA	Are we talking about r.m.s. effective D.C. ? There is ripple associated with three phase full wave rectified D.C. The rms D.C. would not equal peak value of AC unless there is a filter cap on output to keep the peak.

11th November 2009, 02:26 AM	#3
Sceadwian	Doesn't this have something to do with the phase angle difference from each leg? __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har."

12th November 2009, 11:38 PM	#4
RCinFLA	Okay, you forced me to do the calculation. Ignoring rectified voltage drop. 480 vac rms three phase full wave rectified Peak = 678.82 vdc. Minimum = 587.88 vdc Ripple = 90.94 vpk-pk D.C. rms = 648.62 vdc. Last edited by RCinFLA; 12th November 2009 at 11:41 PM.