## Full Wave Bridge Rectifier Circuit

## Full Wave Bridge Rectifier Circuit

(OP)

I have a full wave rectifier thyristor control circuit on a 10 Ohms resistor coil which produced the following results with 240V AC rms.

DC Current through coil (A) DC Voltage across Coil (V) AC Voltage across coil (V rms)

1.15 10.8 92.0

2.43 22.5 153.9

3.44 31.9 189.7

4.63 43.4 211.4

If I reduce the mains input from 240V rms to 110V rms to thyristor full wave rectifier circuit, will I still be able to pull 4.63 Amp DC as the output of a full rectifier circuit is Vrms = Vp / √2, which works out as 110 * 1.414 / √2 = 110 V rms.

DC Current through coil (A) DC Voltage across Coil (V) AC Voltage across coil (V rms)

1.15 10.8 92.0

2.43 22.5 153.9

3.44 31.9 189.7

4.63 43.4 211.4

If I reduce the mains input from 240V rms to 110V rms to thyristor full wave rectifier circuit, will I still be able to pull 4.63 Amp DC as the output of a full rectifier circuit is Vrms = Vp / √2, which works out as 110 * 1.414 / √2 = 110 V rms.

## RE: Full Wave Bridge Rectifier Circuit

Keith Cress

kcress - http://www.flaminsystems.com

## RE: Full Wave Bridge Rectifier Circuit

You are multiplying by a number, then dividing it by the same number expressed in a different way.

" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

## RE: Full Wave Bridge Rectifier Circuit

TTFN (ta ta for now)

I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg

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## RE: Full Wave Bridge Rectifier Circuit

My sketchy maths check,

The Vrms of a full bridge rectifier output is Voltage peak / √2 and the peak voltage of an Vrms = Vrms * √2.

Therefore, 110V Ac rms input to a full bridge rectifier will yield 110V rms at the output, 110 * √2 / √2.

Hi IRstuff,

The reason why raised the question is that when measuring the voltages across the coil when pulling 4.63 A DC is 211.4 V AC and 43.4 V DC.

So reducing the input voltage from 240V rms to 110 V AC rms, the output will only yield 110 V rms so it should be enough for DC current but what about the Vrms AC.

## RE: Full Wave Bridge Rectifier Circuit

The Dc output voltage of a rectifier supplied with 1-phase input and feeding and inductor (a coil) is approximately Vrms * 0.89 when the inductor has enough inductance to cause a constant DC current to flow. So, 110VAC input could get you approximately 98VDC maximum. However, I can't say you will be successful since I have no idea if your coil acts as an inductor or how you made those measurements. I also can't figure out what you did with your measurements to get the a DC voltage so low and a AC voltage so high.

## RE: Full Wave Bridge Rectifier Circuit

And where, pray tell, is this DC current coming from, if not the AC?

A schematic would answer a lot of questions.

TTFN (ta ta for now)

I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg

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## RE: Full Wave Bridge Rectifier Circuit

I was only interested in DC current to the coil but also measured AC as a matter of interest and trying to figure out correlation between AC and DC values.

The measured resistance of the coil was 10 ohms so I assume DC voltage and DC current relates to resistance of the coil and AC voltage and current to AC impedance of the coil as the rectifier output has AC ripple.

## RE: Full Wave Bridge Rectifier Circuit

From EE101, the source of the DC is the rectified AC, so if you cut your AC by more than half, you'll cut your DC by more than half.

TTFN (ta ta for now)

I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg

FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

## RE: Full Wave Bridge Rectifier Circuit

## RE: Full Wave Bridge Rectifier Circuit

The meter may be sampling 1/2 wave rectified DC.

This would be average rather than RMS.

The meter indicates a value of twice the average further multiplied by a form factor to convert from average to RMS.

Some old analogue multi-meters gave strange results when DC was applied to an AC input.

Bill

--------------------

"Why not the best?"

Jimmy Carter

## RE: Full Wave Bridge Rectifier Circuit

Thyristor strongly implies a phase controlled rectifier. So, since no-one seems to have any idea what phase angle this thing is running at, it's likely time to stop the stupid comments about not remembering EE101 and the effect halving the voltage had.

I already posted what I believe is a sufficient answer, but apparently I have to spell it out. If you want to put 4.63A through a 10 ohm coil then you need 46.3VDC. Assuming this coil has enough inductance, the 110VAC should be capable of producing about 98VDC. You do get that that the possible voltage you can get or 98VDC is > than the voltage you need or 46.3VDC?

Failing to provide enough information for anyone to make a more precise determination, you'll have to try it to see if it works.

## RE: Full Wave Bridge Rectifier Circuit

## RE: Full Wave Bridge Rectifier Circuit

TTFN (ta ta for now)FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg

## RE: Full Wave Bridge Rectifier Circuit

But, you can continue to say it's not possible if you want. With the limited info provided, the only way to know for sure is to try it.

gurse - yes with enough inductance the filter effect causes a constant DC current to flow.

## RE: Full Wave Bridge Rectifier Circuit

I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg

## RE: Full Wave Bridge Rectifier Circuit

If the OP ALREADY has a 1-phase, thyristor or phase controlled rectifier AS HE HAS INDICATED HE HAS, then why would him using what he already has require him to do a blank sheet new design? Do you have some specific reason to doubt he has the system he posted? He's already indicated he could control the voltage and current to the coil with his rectifier, which can't be done using diodes.

## RE: Full Wave Bridge Rectifier Circuit

## RE: Full Wave Bridge Rectifier Circuit

## RE: Full Wave Bridge Rectifier Circuit

## RE: Full Wave Bridge Rectifier Circuit

You specifically asked:

"If I reduce the mains input from 240V rms to 110V rms to thyristor full wave rectifier circuit, will I still be able to pull 4.63 Amp DC"

That isn't a formula, that is a speculation that you will be able to pull 4.63 Amp DC at 110V rms.

Since you are dealing with active electronics, for which you have not specified electrical characteristics, maybe you can. Or maybe you cannot.

## RE: Full Wave Bridge Rectifier Circuit

But Waross pointed out that it could be due to metering errors.

## RE: Full Wave Bridge Rectifier Circuit

Some of the first digital meters looked at the peak value and then indicated a value that assumed that the measured value was a sine wave. If you have one of these maters then AC readings of a chopped DC voltage may be a long way away from reality.

Please describe your meter so that we can confirm or eliminate this possible factor.

Bill

--------------------

"Why not the best?"

Jimmy Carter

## RE: Full Wave Bridge Rectifier Circuit

I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg

## RE: Full Wave Bridge Rectifier Circuit

Attached is the circuit diagram and It is a Fluke 77 series multimeter.

## RE: Full Wave Bridge Rectifier Circuit