Re: Where to buy transformers?

--- In CAD_CAM_EDM_DRO@y..., "ds_hutchins" <hutchins@m...> wrote:

>
> I'm thinking of building my own power supply, and I need to find a
> transformer for a reasonable price.

DeLesley: After having collected surplus equipment for 2 years to
get neat CNC stuff I have a building full of "things". I have
several heavy duty conventional transformers that are for sale at
reasonable prices. Contact me off list about details.

>

?

>
> Also, I've seen several posts that say I should multiply the AC
> voltage by 1.41 to get the DC rectified voltage. In my electronics
> books, however, it says that most AC voltages (such as the 110V
> household voltage) are already specified in rms form. When I'm

buying

> a transformer, do I get a 48V secondary, or a 34V secondary?
>

The RMS (Root Mean Square) voltage is a "average" of an AC signal
(area under the curve). An AC wave actually has its peaks at the top
of the wave form at about 160VAC (1.41 times the RMS of the normal
120VAC line). When you rectify than charge a cap it charges up to
the peak value. If the cap is large enough to take the load and stay
charged by the incomming wave than that is the voltage you will get.
I normal practice the actual DC is slightly less than that but close
enough. So for you answer: a 34V secondary will give you approx
48VDC output at the filter cap.