Newbie question: Center-tap on transformer...

[SpicyBrown]

So uh, yeah. What's the center lead on a transformer for? Consider:
115VAC to 24V. The primary 115V coil has 3 leads. Is the center lead
for ground?

Thanks

 

[dont know]

SpicyBrown wrote:

So uh, yeah. What's the center lead on a transformer for? Consider:
115VAC to 24V. The primary 115V coil has 3 leads. Is the center lead
for ground?

Thanks

are you sure it is the primary? they normally don't have a center tap.

 

[nemo]

dont know <mojo@nospam_netscape.com> wrote in message
news:YTVTb.122478$ef.83925@twister01.bloor.is.net.cable.rogers.com...

SpicyBrown wrote:

So uh, yeah. What's the center lead on a transformer for? Consider:
115VAC to 24V. The primary 115V coil has 3 leads. Is the center lead
for ground?

Thanks

are you sure it is the primary? they normally don't have a center tap.

It might go to a screen - a layer of copper foil between the primary and the

secondary. Put a meter on it set to Ohms and if it's open circuit to all
other connections it'll be a screen.

Nemo

 

[SpicyBrown]

Actually you're right, sorry. Its a 115vac to 24vct - so the secondary
coil has the centertap. I can't seem to find anything about
transformers online beyond what I already know - nothing about the
center tap..

It's being used to supply a variable DC power supply btw, so the
transformer will feed directly into a bridge rectifier.

-SpicyBrown


On Tue, 03 Feb 2004 23:10:48 GMT, "dont know"
<mojo@nospam_netscape.com> wrote:

SpicyBrown wrote:

So uh, yeah. What's the center lead on a transformer for? Consider:
115VAC to 24V. The primary 115V coil has 3 leads. Is the center lead
for ground?

Thanks

are you sure it is the primary? they normally don't have a center tap.

 

[JeffM]

so the transformer will feed directly into a bridge rectifier
SpicyBrown

There are 2 kinds of full-wave rectifiers:
bridge (4 diodes) and center-tapped (2 diodes).
http://images.google.com/images?num=100&hl=en&lr=lang_en&ie=UTF-8&oe=UTF-8&safe=off&q=full-wave+bridge+center-tapped&sa=N&tab=wi

If you have a bridge and center-tapped transformer,
it would seem likely that you have a positive and a negative supply
with a common return.
Otherwise, half of the bridge is unused or the center tap is not used.