Re: HELP With Step-Down Transformer and Converter

On 18 Sep 2005 07:00:19 -0700, "gene" <winapps2@xxxxxxxxxxxxxxx>
wrote:

>Dear Phil & Phantom,
>
>There is no particular application.
>I'm trying to test Faraday's Induction Laws.
>I want to built a similar device but also test the limit of how much
>maximum current can be generated in a DC-DC Step-Down Converter.
>
>Thanks.
>
>Gene

OK, Gene. I don't understand why you have to test at such high
currents, but here goes. The 60 Hz transformer will be much easier.
You will need a transformer capable of handling about 3000 watts, with
a bobbin. You will need a square stack of what are known as EI250
laminations. You will need to wind *about* 200 turns of wire of
appropriate gauge (fill about half the bobbin) for a primary. Then
the secondary will need to consist of copper conductor of about 1
square inch cross section (I calculate that you will need to use about
10 lengths of 2/0 cable in parallel). Thread the 10 pieces of 2/0
wire in parallel through the space remaining on the bobbin (that's one
turn). This secondary will be able to handle about 3000 amps
continuously (I say continuously with tongue in cheek. You could be
dissipating upwards of 3000 watts. Things are going to get hot
quickly). You will only have about a volt, so you can't get the 3000
amps through much of anything other than a dead short of the
secondary. The leakage inductance of such a transformer may prevent
getting the full 3000 amps, but it will give you a start.

You must put a current limiting resistor in series with the primary if
you are going to run with a shorted secondary; perhaps a big light
bulb. Put a 500 watt incandescent bulb in series with the primary; if
that doesn't give you enough current (put an ammeter in series with
the primary), put another bulb in parallel with the first, adding more
as needed. Be aware that finding 240 volt 500 watt bulbs may be
difficult. You could perhaps use 300 watt, 120 volt bulbs, which are
fairly common at regular stores, with two of them in series to stand
off 240 volts. Put multiple two-bulb combinations in parallel to get
the needed current in the 240 volt primary.

Try not to hurt yourself, or burn down the house!

.

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