[TriEmbed] Inexpensive 120V (15A) to 240V (7.5A) transformer?

[Robert Gasiorowski]

Get any 240V, 1kW transformer with dual primary (2 x 120V.)
Make one side common, connect center to 120V, the second side will give you
240V (non-isolated.)
You will end up with what's called autotransformer. ATs are much smaller
than isolating transformers.
I used this type of transformers to power US made appliances like microwave
ovens in EU (220V->110V.)

On Tue, Apr 12, 2016 at 6:45 AM, Josh Wyatt via TriEmbed <
triembed at triembed.org> wrote:

> What are your power requirements?
>
> A few ideas...
>
> 1. If all you need is high voltage DC for charging a battery bank, you
> could use a voltage doubler. Check out the full wave circuit here:
> http://www.daenotes.com/electronics/devices-circuits/voltage-multipler
>
> 2. You could buy two identical 120vac-to-12vac transformers and use one
> for boost. Connect transformer 1 in the conventional way, to provide 12vac.
> Connect the 12vac output of transformer 1 to the 12vac winding of
> transformer 2; the "output" of transformer 2 will now have 120vac which you
> can place in series with your line voltage for 240vac. (make sure it's in
> phase or you'll get 0 volts out).
>
> 3. Alternatively, search ebay for 'control transformer,' as this is a
> pretty common need and application in the electrical world. Be sure to
> choose it properly for the voltages and power you expect. For example,
> http://www.ebay.com/itm/Square-D-9070T150D1-Industrial-Control-Transformer-SCHNEIDER-ELECTRIC-/272208984055
>
> Lastly - It goes without saying, but be careful; you're dealing with
> lethal voltages here.
>
> Thanks,
> Josh
>
> On Mon, Apr 11, 2016 at 11:14 PM, Kevin Schilf via TriEmbed <
> triembed at triembed.org> wrote:
>
>> Hi Phil,
>>
>> I don't know what Shane has in mind, but that is an interesting idea
>> about using two receptacles; although, Mr. Murphy will probably ensure that
>> opposite phase receptacles will be several feet apart as you note.  :-)
>>
>> Why not just add a two pole, 240V circuit breaker assuming you have space
>> in the panel and can reasonably run wire from your load to the panel?
>>
>> BTW, I think there may be a typo in your email, should be:
>>
>> AWG 10 -> 30 A
>> AWG 12 -> 20 A
>> AWG 14 -> 15 A
>>
>> To anyone reading this post, same impedance at twice the voltage = 4
>> times the power delivered.  Please be careful and consult a licensed
>> electrician if in doubt.
>>
>> Sincerely,
>> Kevin Schilf
>>
>> ------------------------------
>> *From:* Phil Smith via TriEmbed <triembed at triembed.org>
>> *To:* Shane Trent <shanedtrent at gmail.com>; TriEmbed Discussion <
>> triembed at triembed.org>
>> *Sent:* Monday, April 11, 2016 6:59 PM
>> *Subject:* Re: [TriEmbed] Inexpensive 120V (15A) to 240V (7.5A)
>> transformer?
>>
>> If you can find outlets close to each other whose hots (x and y) are from
>> adjacent circuit breakers, then you could combine x,y, and g (ground) using
>> two plugs to get 240V, although the outlets are likely only rated at 120V,
>> 15A (14 AWG wire).  Another way of looking at it is x=+120V, y=-120V
>> (relative to Neutral n here n ~= g except at high current draw.  Often
>> wiring within a single residential room is from a single circuit breaker.
>> Interestingly, the National Electric Code (NEC) rates 10, 12, and 14 AWG
>> wire at 15,20, and 30 amps no matter how long the wire is, analogous to the
>> state of SC once legisilating the value of pi to be exactly three.  AWG<10
>> wire is not subject to this arbitrary amperage and equations for resistance
>> and reactance are used instead.
>>
>> Phil
>>
>>
>> On Monday, April 11, 2016 5:16 PM, Shane Trent via TriEmbed <
>> triembed at triembed.org> wrote:
>>
>>
>> Hey all!
>>
>> I am looking for a transformer to setup 120V up to 240V. I recall seeing
>> a transformer company at the Hamfest last year but do not remember the
>> name. Can anyone recommend a vendor? Does not have to be a high-end design.
>> Is powering a charging system that corrects for variations in line voltage.
>>
>> Thanks for any suggestions!
>>
>> Shane
>>
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>
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