Transformer notation

happy hippy · 22nd January 2012, 10:29 PM

Hi there,

Back again with another question, from my ignorance. Attached are two transformer schematics. They both have rectifiers coming off the secondaries. The question is one of these center tapped or both? I'm in the process of figuring out what transformer to buy, and the nomenclature is confusing.

Thanx
The Happy Hippy

happy hippy · 22nd January 2012, 10:35 PM

Lets hope the atachments attach this time.

Thanx
The Happy Hippy

zigzagflux · 22nd January 2012, 11:01 PM

1 is providing isolated power supplies with its two secondary windings.
2 is essentially doing the same thing, but there is no isolation. Also, the common is not at the same potential, so this configuration is a little odd and non-traditional.

Both of these xfmrs could be used as a center tapped transformer if connected properly. If you want a +/- dual supply, you only need a total of 4 diodes with a center tap. Do not wire as per #2. #1 could work, but is a little wasteful of voltage and has extra diodes.

pdul · 22nd January 2012, 11:02 PM

trans 2 is centertapped and trans1 is two secondaries

happy hippy · 22nd January 2012, 11:20 PM

OK What I need is one transformer, putting out two DC voltages, the second voltage twice as much as the first. So don't I need both rectifiers?

The Happy Hippy

dtproff · 23rd January 2012, 09:47 AM

Is this for the AC Mains?

DF96 · 23rd January 2012, 10:26 AM

Tell us what you are trying to achieve. Your post 5 could be interpreted as a requirement for two DC voltage rails, one at twice the voltage of the other. If so, you need a CT secondary (or two separate identical secondaries, wired as a CT), one bridge and pairs of caps. Wire the reservoir caps like a dual +- supply, ground the -ve instead of the '0V'', then add the resistors and smoothers to the voltage rails.

AndrewT · 23rd January 2012, 11:30 AM

Dual secondary is one way of winding a transformer.
Two independent windings that are isolated from each other.
This would be specified as 0-20, 0-20Vac, or dual 20Vac
Centre tapped is an alternative way of winding a transformer.
one long winding that has a tapping in the centre. This results in a winding that has 3 "tails". They are not isolated from each other. Since one of tails is connected to the centre/middle of the long winding the voltages in either half of the winding are identical. This is usually specified as 20-0-20Vac or as 40Vac centre tapped.

happy hippy · 24th January 2012, 12:03 AM

OK! Thats what I needed to know. Thank you all very much.

Thanx
The Happy Hippy

22nd January 2012, 11:20 PM	#5
happy hippy diyAudio Member Join Date: Jan 2010	Still confused OK What I need is one transformer, putting out two DC voltages, the second voltage twice as much as the first. So don't I need both rectifiers? The Happy Hippy __________________ When all else fails, read the instructions.

23rd January 2012, 11:30 AM	#8
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Dual secondary is one way of winding a transformer. Two independent windings that are isolated from each other. This would be specified as 0-20, 0-20Vac, or dual 20Vac Centre tapped is an alternative way of winding a transformer. one long winding that has a tapping in the centre. This results in a winding that has 3 "tails". They are not isolated from each other. Since one of tails is connected to the centre/middle of the long winding the voltages in either half of the winding are identical. This is usually specified as 20-0-20Vac or as 40Vac centre tapped. __________________ regards Andrew T.

24th January 2012, 12:03 AM	#9
happy hippy diyAudio Member Join Date: Jan 2010	OK! OK! Thats what I needed to know. Thank you all very much. Thanx The Happy Hippy __________________ When all else fails, read the instructions.

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22nd January 2012, 10:29 PM	#1
happy hippy diyAudio Member Join Date: Jan 2010	Transformer notation Hi there, Back again with another question, from my ignorance. Attached are two transformer schematics. They both have rectifiers coming off the secondaries. The question is one of these center tapped or both? I'm in the process of figuring out what transformer to buy, and the nomenclature is confusing. Thanx The Happy Hippy __________________ When all else fails, read the instructions.

22nd January 2012, 11:01 PM	#3
zigzagflux diyAudio Member Join Date: Oct 2006	1 is providing isolated power supplies with its two secondary windings. 2 is essentially doing the same thing, but there is no isolation. Also, the common is not at the same potential, so this configuration is a little odd and non-traditional. Both of these xfmrs could be used as a center tapped transformer if connected properly. If you want a +/- dual supply, you only need a total of 4 diodes with a center tap. Do not wire as per #2. #1 could work, but is a little wasteful of voltage and has extra diodes.

22nd January 2012, 11:02 PM	#4
pdul diyAudio Member Join Date: Jan 2009	trans 2 is centertapped and trans1 is two secondaries

23rd January 2012, 09:47 AM	#6
dtproff diyAudio Member Join Date: Oct 2008 Location: Plano, TX, USA	Is this for the AC Mains?

23rd January 2012, 10:26 AM	#7
DF96 diyAudio Member Join Date: May 2007	Tell us what you are trying to achieve. Your post 5 could be interpreted as a requirement for two DC voltage rails, one at twice the voltage of the other. If so, you need a CT secondary (or two separate identical secondaries, wired as a CT), one bridge and pairs of caps. Wire the reservoir caps like a dual +- supply, ground the -ve instead of the '0V'', then add the resistors and smoothers to the voltage rails.

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