DC output from a bridge rectifier.

[Rampage]

Been thinking about this. From standard UK 50Hz 230 Uo into a bridge rectifier the output would be 'b' on the drawing below?
Thanks.

 

[Knobhead]

RMS applies to single phase as well

Phase to phase voltag is phase to neutral * √3

 

[tazz]

Tony you are totally correct, but i cant think of an example to explain

 

[Knobhead]

So that's where the 1.414 comes from! I never realised it's the square root of 2!
The inverse being 0.707

Still a bit confused though, is the RMS from the output of the bridge rectifier still 230v? Or does RMS not apply to DC? Meaning it could be called 325v rippled?

For full wave rectification the mean value is the RMS value, you will start to get near peak value if you start to introduce capacitors.
Somewhere I've got some drawings that may help. Somewhere being the operative word!

For three phase chuck RMS out of the window! It gets nearer to peak voltage.

 

[Knobhead]

Typical I've got three phase but not single.

View attachment 14597
3 phase full wave rectification. you can see the sharp change over from one diode to the next.

 

[Knobhead]

I'll do some singe phase drawings for you, but it won't be tonight.

 

[tazz]

Tony real interesting, imformative post and very well put...thanks

 

[Rampage]

I'll do some singe phase drawings for you, but it won't be tonight.

Thanks very much

 

[Knobhead]

Tazz, I've enjoyed doing it. It's made a change from some of the dire threads we've had recently.

Will do the drawing for the single phase, it's only a case of egiting drawings I've already done.

- - - Updated - - -

You as well Rampage :yes:

 

[thekingiam]

cant see what you are tring to work out single phase?

 

[thekingiam]

ok read post again, found pic on google have a better one somewhere makes a bit more easier for lamen. done btec electronics before realising wasn't for me so took electrical a long long time ago more electronic questions for a change but not too difficult please.

 

[Knobhead]

Right here we go:

View attachment 14600
Single phase wave form

View attachment 14601
Single phase wave form half rectified

View attachment 14602
Single phase wave form full rectified

View attachment 14603
Three phase wave form

View attachment 14604
Three phase wave form half rectified

View attachment 14605
Three phase wave form full rectified

You can see the fully rectified three phase will give a fairly smooth DC compaired to single phase

These two show the useful power from single and three phase fully rectified supply

View attachment 14607

View attachment 14606

 

[Rampage]

Thanks for that, it's been a busy week, hopefully I'll find some time to look at the diagrams tomorrow!

 

[johnboy6083]

for information RMS (root mean squared) is used in AC because it relates to an amp per volt that will acheive the same heating effect as 1 amp per volt in a DC system.

Im trying to find a link for this, as its something i covered in college years ago.

 

[johnboy6083]

EDIT: try this link: http://www.google.co.uk/url?sa=t&rct=j&q=rms%20heating%20value&source=web&cd=1&cad=rja&ved=0CCAQFjAA&url=http%3A%2F%2Fen.wikipedia.org%2Fwiki%2FTrue_RMS_converter&ei=3_tbUO-nB-em0QWNq4CYBg&usg=AFQjCNFJmQ6nZLAPEjiWI8fJ95dBVl71rg

 

[Knobhead]

I've just completed a spreadsheet to calculate it.
It can be used for waveforms other than sine, also ripple and superimposed waveforms such as rectified 3ph.