|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
108.253.181.30
In Reply to: RE: Transformer secondary measurement posted by Cleet Torres on August 03, 2013 at 22:15:05
From your example, you have a dual secondary. Normally, the primary and secondary do not have any kind of direct connection to each other or ground.Sometimes there is a green ground lead making connection to the iron laminations of the transformer,so in case the insulation breaks down on either the pri or sec, the chassis the transformer is bolted to doesn't become energized. (However, your transformer has a ferrite core, and ferrite cores are not electrically conductive.)
What might be confusing you is that on tapped secondary power transformers, (Many power supply designs have transformers with a tapped secondary), the center lead is connected to either ground or a circuit ground, then the two other leads connect to diodes to rectify the AC current to DC. This example is a power supply. If you have a power supply with a center-tapped transformer secondary design, you can usually measure identical ohms readings between the center tap and the other secondary leads. Of course, you don't want to energize the the transformer while taking any ohms readings.
BTW, if you connected the two "inner leads" of your dual secondary trsnsformer, and then measured the voltage output of the two "outside leads" (the two secondaries would be connected in series), you should measure twice the voltage as in measuring just one secondary. This of course, assumes that both secondaries are identical. Now if you measured both secondaries connected to each other in parallel, (reminder, you have to connect them in the proper phase for both series and parallel connections), you would get the same voltage, but twice the current output.
"The Blues isn't about feeling better. It's about making other people feel worse and making a few bucks while you're at it" "Bleeding Gums" Murphy
Edits: 08/05/13 08/05/13 08/05/13 08/05/13 08/05/13Follow Ups:
Hi Tesla
Thanks for your response.
I've don't have a dual secondary; two wires into the primary side 115V, and two wires out the secondary 25V.
Now on the primary side I get a hot and neutral in from the mains, right? I was wondering if the output on the secondary would be the same i.e. one hot, one neutral?
I'm thinking on the secondary both lines would be hot, and the voltage across the lines would be 25VAC. In short, my input to the primary is unbalanced, but the out would be balanced. (Unless of course I tie one of the outputs to ground that is)
Thanks
Cleet
Cleet, you are right.
The primary from the house wiring will be 110 to 125 volts ac, and facing the outlet, the right hand slot will be hot, obviously the left hand will be cold, (Neutral) and the center will be safety ground.
The output (secondary) will be 25vac from lead to lead, just as you said.
Hope this helps.
Gene
"The Blues isn't about feeling better. It's about making other people feel worse and making a few bucks while you're at it" "Bleeding Gums" Murphy
Hi Gene.
Yep, it sure does. Thanks
It seems to me that we cannot comment on the voltage of the individual wires from the secondary as we need some reference to measure the voltage from, and the only reference we have is the other output cable. Hence the “only” voltage measurement we can make is between the two cables which is 25VAC?
Years ago I saw an old schematic (probably circa 1950 – 1960?) where a center tap was derived by grounding both output leads individually through a pair of resistors to a common ground , rather than shorting one of the outputs directly to ground as is the more common approach.
I don't see anything like that on schematics I find online, so I assume that was a dangerous practice? I was thinking I could perhaps do that, have the output grounded and balanced rather than grounded and unbalanced.
So in my case, I could use a 12.5 ohm resistor per side, ground the output individually to ground via a resistor, and then achieve a 12.5VAC from each cable to ground?
Bad idea?
Thanks
Cleet
I suggest you read this, and look for additional sources on the internet as needed.
There are many different transformers, many different kinds of circuits using transformers, and hopefully this will help you understand them, and their applications better.
Here are so more images of transformer power supply schematics, from Google, and the examples shown may be easier to follow.
http://www.google.com/search?q=transformer+power+supply+schematic&tbm=isch&tbo=u&source=univ&sa=X&ei=MkcEUviqJKa-igKRj4GgDQ&ved=0CCoQsAQ&biw=1024&bih=601
"The Blues isn't about feeling better. It's about making other people feel worse and making a few bucks while you're at it" "Bleeding Gums" Murphy
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: