Re: [CAD_CAM_EDM_DRO] Power supply question.....

scott wilson wrote:

> if you have a good low ohm scale on meter you should be able to figure out internal config
>
> Raymond Heckert wrote:
>
> > If you have only 3 wires on the secondary, and get 28v from start wire to
> > the tap, and 32v from start to finish, then it's not a ct (center-tapped)
> > transformer, just a tapped transformer. If there are 5 wires, then it's
> > probably a tapped bi-filar, with a common center-tap. That's all I can
> > surmise from your description.

Not always true. If a true CT winding (ie equal number of turns from CT to
each end) is wound with one half out to CT, then other half wound on top, the
second half will have MUCH higher DC resistance than the first half, because
the circumference of the outer winding layers is larger. This is VERY common
practice in power transformers, and has minimal effect on the power supply.
But, it can be VERY confusing when you see a 2:1 difference in the DC
resistance, but the AC voltage output from each half of the winding is the
same.

Jon