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Old 24th November 2011, 11:32 AM   #741
AndrewT is offline AndrewT  Scotland
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The output of a transformer can be predicted with just a few bits of the manufacturers' data and one formula.

Output DC voltage after smoothing with no load on the output is given by Vdc = [Vmains / Nominal Vmains * rated Vac of secondary * (1+transformer regulation) * sqrt(2) ] - [diodes Vdrops at near zero diode current].

For a 9.5% regulation 230:15+15Vac transformer running on 236Vac with ordinary bridge rectifier.
Expect the prediction to give
{236 / 230 * (15+15) * (1+0.095) * 1.414} - {2*0.5} ~46.7Vdc

With the correct information the application of the formula allows the model to predict the expected DC voltage. It really is that simple.
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Last edited by AndrewT; 24th November 2011 at 11:35 AM.
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Old 24th November 2011, 06:45 PM   #742
RCruz is offline RCruz  Switzerland
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Quote:
Originally Posted by AndrewT View Post
The output of a transformer can be predicted with just a few bits of the manufacturers' data and one formula.

Output DC voltage after smoothing with no load on the output is given by Vdc = [Vmains / Nominal Vmains * rated Vac of secondary * (1+transformer regulation) * sqrt(2) ] - [diodes Vdrops at near zero diode current].

For a 9.5% regulation 230:15+15Vac transformer running on 236Vac with ordinary bridge rectifier.
Expect the prediction to give
{236 / 230 * (15+15) * (1+0.095) * 1.414} - {2*0.5} ~46.7Vdc

With the correct information the application of the formula allows the model to predict the expected DC voltage. It really is that simple.
Thank you Andrew.

You made it very clear as usual

But i have sme questions:

What is the relation between Efficiency and regulation ?

I have a 230V toroid with 89% Efficiency
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Last edited by RCruz; 24th November 2011 at 07:09 PM.
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Old 25th November 2011, 08:59 AM   #743
AndrewT is offline AndrewT  Scotland
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That efficiency will be quoted for one output power only.
Similarly the transformer regulation is stated for one output power only. The regulation applies to the ratio between maximum rated output power and zero output power.
The efficiency of a transformer varies markedly over the output power range.
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Old 25th November 2011, 12:27 PM   #744
RCruz is offline RCruz  Switzerland
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I can not find any information about regulation in the TX specs I normally use.

I know the lower the value the best, but to have a low percentage of regulation factor, the number of turns in the primary must also be very low.

What should be the average number for a R-Core 120VA 220V to 30V TX ?
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Old 25th November 2011, 03:43 PM   #745
Marra is offline Marra  United Kingdom
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Finally getting round to wiring up the bib to power my Optivol board and wondered does the regulator need connecting to chassis ground and if so where is the best place on the reg pcb to connect to? Thanks
Found it post 369

I used a 9Vac secondary to give me the 5Vdc output and used a 6R8 resistor to achieve 198ma[1.34V drop] with 3 green led's. Everythings runs warm but you could hold your finger on things all day. Still sounds good.

Last edited by Marra; 25th November 2011 at 03:52 PM.
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Old 26th November 2011, 09:05 AM   #746
AndrewT is offline AndrewT  Scotland
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Default correction to post

Quote:
Originally Posted by AndrewT View Post
The regulation applies to the ratio between maximum rated output power and zero output power.
regulation applies to the voltage ratio between maximum rated output power and zero output power
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Old 26th November 2011, 03:25 PM   #747
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Quote:
Originally Posted by merlin el mago View Post
With a tx 9VAC 30VA could I get 5V 1A?
Quote:
Originally Posted by AndrewT View Post
yes
R301 1R5
Vref 1K trimmer + 1 red LED, other parts jumped

I can't reach 5Vout?

Have I to connect 1K resistor in R303 (Vref area)?
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Old 26th November 2011, 04:09 PM   #748
Tea-Bag is offline Tea-Bag  United States
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Default BiB Kit reference voltages Blog started

Hey there, for those of you who have completed target voltages and current, I have created a blog entry to centralize the parts lists needed. Please, please add your stuff into the blog, so others have a place to look get an idea of what parts they need for a particular project.

You can either add to the blog in a reply, or PM me the stuff, and I will edit it into the ugly main page...

Here is the URL
http://www.diyaudio.com/forums/blogs...-voltages.html
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Old 26th November 2011, 04:45 PM   #749
AndrewT is offline AndrewT  Scotland
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30VA / 9Vac = 3.3Aac.
Max continuous DC current from a capacitor input filter is 3.3 / 2 = 1.67Adc.
Your 1A will use up 60% of the maximum continuous rating.

9Vac * sqrt(2) * ~1.3 (regulation) * 0.94 (mains low voltage) - bridge rectifier ~ 13.5Vdc.
Vdrop to output voltage ~8.5V
What's the problem?
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Old 26th November 2011, 05:20 PM   #750
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When I connect the E-MU 0404 can't reach 5Vout
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