What happen in I connect the tranformers windings in serie?

[Lac]

Hi there!
I have got this transformer that has got these specs:

4.5 VA dual secondary voltage

Full load 2×6V
Unloaded 2× 9.2V
Max.current 2×375mA

Would that mean that if i connect the secondary windings in serie, i would get these specs?:

Full load 12V
Unloaded 18.4V
Max.current 750mA

Thanks.

 

[TheOne]

No, voltage would double and current stays the same as for one winding. In parallel voltage stays the same and current double.

 

[Lac]

ohh. just like batteries, I see. thanks!

 

[k7elp60]

I would add that in order for the voltage to add the windings must be phased properly, otherwise the output voltage will be 0.

 

[panic mode]

...and if you try to parallel secondaries for more current but don't watch phases, it will smoke...
before paralleling, connect in series and measure voltage on ends.
if it is next to nothing, it is safe to connect the ends (keep the "middle" or tap connected the way it is). If you see that voltage accross ends is sum of the two secondaries, you have to swap the ends of ONE of the secondaries (not both).
also don't try to parallel different secondaries...

you can also connect in series primary and secondary too. it's called autotransformer. so if you have 120VAC primary and 40VAC secondary, you can get voltages like 80VAC (120-40=80) or 160V (120+40=160) depending on arangement. note that in this case there is no isolation from the mains but the transformer size can be much smaller than isolated version for same power rating.