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Old 28th June 2011, 02:59 PM   #1
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Default Two bridges and a CT transformer....

Good morning all...
Sorry for my poor drawing ability, but will this work?

Thanks,
Ray
rsumperl@hhk.com
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Old 28th June 2011, 03:02 PM   #2
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What are you trying to achieve?
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Old 28th June 2011, 03:12 PM   #3
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The bridges feed voltage regulators, however the regulators are different from each other.
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Old 28th June 2011, 03:20 PM   #4
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Are you trying to regulate both positive and negative voltages?
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Old 28th June 2011, 03:45 PM   #5
DF96 is offline DF96  England
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As drawn it will not work, unless you are trying something strange. A CT secondary should normally feed just one bridge. Tell us what you want to do, and then we can tell you how to do it.
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Old 28th June 2011, 03:52 PM   #6
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Originally Posted by DF96 View Post
As drawn it will not work, unless you are trying something strange. A CT secondary should normally feed just one bridge. Tell us what you want to do, and then we can tell you how to do it.
and why not? just trying to understand
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Old 28th June 2011, 03:55 PM   #7
ChrisA is offline ChrisA  United States
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Quote:
Originally Posted by rsumperl View Post
Good morning all...
Sorry for my poor drawing ability, but will this work?

Thanks,
Ray
rsumperl@hhk.com
The usual reason people use two bridges on a CT transformer is to have a plus and minus supply but you are using the plus side of both bridges. You can have the same result with just two diodes in place of the eight you are using. I can't think of one reason to do what you have drawn.

OK I read about feeding two regulators. I still can't figure why each regulators would need it's own bridge. It is better not to use a bridge because it wastes power with two diodes in series, so you have double the voltage drop in the rectifier

Last edited by ChrisA; 28th June 2011 at 03:59 PM.
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Old 28th June 2011, 03:58 PM   #8
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It will work as long as the two outputs are totally isolated from each other. Connect any of the output terminals to another or to a common point such as ground and you'll have a short circuit. A single bridge can give you positive and negative supplies with a center-tapped transformer.
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Old 28th June 2011, 04:00 PM   #9
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What is the specification of the transformer (ie 12-0-12VAC 50VA).

What voltages and currents are you trying to achieve ?
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Old 28th June 2011, 04:14 PM   #10
DF96 is offline DF96  England
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Let us assume for the moment that the CT is grounded. It may not be, but we have to establish some voltage reference as all voltages are with respect to some other voltage.

Then the - leg of the upper supply will sometimes be floating, sometimes be connected to the CT via a diode drop, and sometimes connected to the upper sec output via a diode drop. Conversely for the + leg. Similarly, only opposite, for the lower supply. Hence all your supplies will be whizzing up and down at line frequency. I assume this is not what is wanted - most people want a DC supply to be referenced to a fixed point (often ground).
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