RE: [CAD_CAM_EDM_DRO] current rating of transformers

Jon:

I could be wrong, but I think you're confusing transformer output with
stepper input here...:)

If I am correct, the current rating in a transformer has mostly to do with
the gauge wire used, and if half the winding can take 10A, so can the full
winding.

I can't find the catalog page that he is referring to(or at least the part
about the "cap"), but it sounds to me like they are telling you how to
determine what capacitance or inductance to use for filtering of the power
supply that you build with this transformer, based on the output current
required.

Andy Wander
Verrex Corporation


-----Original Message-----
From: Jon Elson [mailto:elson@...]
Sent: Sunday, October 24, 2004 12:26 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] current rating of transformers


turbulatordude wrote:

>Hi,
>
>If I have a 24 volt, (12V-0-12) center tap transformer like the MPJA
>unit.
>http://www.mpja.com/productview.asp?product=7846+TR
>
>And isolate the center tap I get 24 volts.
>
>But when rectified, doesn't the current change also ?
>
>There is a note in the catalogue that for this wiring the amps are
>1.8x
>
>The catalogue refers to required ouput amps
>
>
>full wave bridge cap input filter 1.8x to required output amps
>full wave choke input filter = required output amps
>full wave, center tap, cap = 1.2x roa
>full wave, center tap, choke = 0.7x roa
>
>

Using the full winding means current flows in both ends of the winding
all the time. So, the current rating must go down. With full-wave
center tap, each half of the winding gets a rest 50% of the time, so
current rating goes up. I guess what they are saying here is that you
take the load current and multiply by these factors to get the rating
of the transformer.

Jon



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