Conor Bryan

Hi Folks, I believe I 'might have been off that day in collage' but can anyone explain the theory of the center tap on the secondary winding on a transformer. It's melting my head. If this is connected to the secondary windings should we not get a dead short?? What am I missing?? Hope you can help.

waco

The center tap serves to create two secondaries on the same transformer and won't be seen as a short because the secondary windings and the attached load still serve to limit current.

Transformer theory is are hard for most people to visualize because it is usually taught using "frozen" waveshapes when really, the voltage is constantly rising and falling and changing polarity. Best to just go with the conclusion without trying to visualize the device at frozen moments which convert the AC into DC.

Draw a secondary winding, assign polarities at the top and bottom (negative and positive) than draw a center tap. The polarities at the center tap will be as if you had batteries in series, meaning the positive end of the secondary will be more positive than the center tap, but not as negative as the negative end of the transformer.

I doubt that helps, but it always worked for me.

Conor Bryan

Hi Waco and thanks for your reply. I have to admit I'm still a little confused. I'm struggling to get a clear picture in my head and I suppose the fact that I've never worked close to transformers being assembled and have never physically seen this tap doesn't help me to try to understand. Are there any photos or schematics that you know of that might help me. Even the fact that you said it creates 2 secondaries has thrown me even more.

Sorry

waco

I'm not good at graphics and what not, but if you add a line to the center of the secondary in this schematic, then you have a center tapped transformer and each "side" of the secondary acts like a separate transformer in some ways, but each "side" of the secondary can and does still conduct through the other side at certain times.

As I wrote, at any given time, the polariy of the secondary will be plus at the top (let's say) and negative at the bottom, so the center tap will be not as positive as the top, but more positive than the bottom. Therefore, it will not be as negative as the bottom, but still more negative than the top.