Re: [CAD_CAM_EDM_DRO] Transformer Soft Start

Jon,

I agree.with you. Likely problems I'd be concerned about:

1) Transformer is actually shorted
2) Split 230/115 primary is wired with one of the primary coils reversed

If the transformer is shorted, you probably can't tell with an
ohmmeter. Even a single loop that is shorted will cause the current to be
too high. In effect, a single shorted loop looks from the primary AC side
as if the primary is shorted. There could be several ways to test for this
with an ohmmeter. One might be to connect a 9V battery to one coil, and
watch in the dark for a spark as the battery is removed. A shorted
transformer won't make a spark, but a working one MIGHT. A good, healthy
spark would be a good indication that the transformer itself is OK.

I like your idea of a 220V bulb, and would use that to test the primary
phasing. I'd disconnect the secondary winding completely, and leave it
open. I'd connect the primaries in series, and also in series with the
bulb. If the light is lighting (after a few seconds) after applying AC
through the bulb, I'd reverse one of the primary coils and try again. If
the light goes out, the transformer is not shorted, and the primaries are
phased correctly. If the light stays on both ways, then the transformer is
bad.

-- Carl

At 10:42 AM 7/3/2003 -0500, you wrote:

>tiffyted wrote:
>
> >Can anyone in this group advise me on a suitable circuit for soft
> >starting a 230v primary, 40v secondary 1000VA toriordal transformer.
> >
> >I have one I want to use with my Gecko 201's, but it keeps blowing
> >the mains fuze on power up.
> >
> >
> >
>I think you have something serious wrong, here. I don't think soft start
>will help you. it is possible the transformer is defective. Are you sure
>it has a 230 V primary? Is it a split primary, 2 coils that can be
>wired for either 115 or 230 V? If so, an incorrect connection in either
>setting will blow fuses. The phase of the two windings must be correct
>for it to work.
>
>First, I'd disconnect the secondary wires and see if the problem still
>ocurrs. If not, then most likely the rectifier is bad or wired wrong.
>If it still blows, you need to check the primary wiring with the
>manufacturer,
>or with someone who has successfully used the same transformer on 230 V.
>
>If you can't get any help on this, wire a 230 V light bulb in series with
>the transformer primary. If the bulb glows at full brightness, the
>transformer
>must be appearing as a short. With the recifier/capacitor connected, it
>should glow brightly for a few seconds, and then begin dimming as the
>capacitor slowly charges.
>
>Jon
>
>
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