Re: [CAD_CAM_EDM_DRO] Re: Power supply

He's saying that the output from the buck transformer should be
connected on the *primary* of the larger transformer, to reduce the
input voltage by roughly 10%.

In that case, 4A in the primary of the main transformer (and the
secondary of the buck transformer) would allow roughly 440W at the
secondary (I think he forgot to subtract the 12V from the input voltage,
so it's 4 * 108 = 436W)

This will reduce the final output voltage by only about 6V, rather than
a 12V reduction if it were on the secondary.

- Steve

Peter Reilley wrote:

>A .05 KVA transformer that is driving a perfectly
>resistive load is capable of supplying 50 Watts.
>There is no getting around that 50 Watt limit.
>Volt-Amps (VA) is the same as Watts for a
>resistive load.
>
>This transformer can supply about 4 Amps at
>12 volts or about 2 Amps at 24 volts. It will
>draw about .4 Amps if the primary is wired
>for 120 Volts or about .2 Amps at 240 Volts.
>
>>From this it can be deduced that the wire used
>in each of the two secondaries is capable of carrying
>about 2 Amps. The wire in each of the two
>primary windings is capable of carrying .2 Amps.
>You cannot exceed these current limits without burning
>up the transformer.
>
>Pete.
>
>
>
>
>----- Original Message -----
>From: "David Speck" <Dave@...>
>To: <CAD_CAM_EDM_DRO@yahoogroups.com>
>Sent: Saturday, June 24, 2006 11:49 AM
>Subject: Re: [CAD_CAM_EDM_DRO] Re: Power supply
>
>
>
>
>>Peter,
>>
>>It's true that the buck transformer is rated at 4 amps, but if applied
>>to the primary side of the power circuit as is usually practiced, then
>>that means you would be drawing 4 amps through the 120 volt primary, or
>>delivering about 480 watts to the secondary of the original
>>transformer. The original enquirer didn't spec the size of the original
>>transformer, but 480 watts sounds like a reasonable initial guess.
>>
>>Dave
>>
>>Peter Reilley wrote:
>>
>>
>>>That transformer is not adequate.
>>>It is spec'ed as .05KVA. That means that it is good
>>>for about 4 Amps when wired for 12 Volts.
>>>
>>>Pete.
>>>
>>>----- Original Message -----
>>>From: "David Speck" <Dave@...>
>>>To: <CAD_CAM_EDM_DRO@yahoogroups.com>
>>>Sent: Saturday, June 24, 2006 10:39 AM
>>>Subject: Re: [CAD_CAM_EDM_DRO] Re: Power supply
>>>
>>>
>>>
>>>
>>>
>>>>This buck / boost transformer would do the job for $29.99 w/ $10.00
>>>>shipping on eBay's "Buy it Now"
>>>>
>>>>Dave
>>>>
>>>>GE BUCK BOOST TRANSFORMER CATALOG# 9T51B0102 Item number: 3853854254
>>>>
>>>>====+====+====+====+====+====+====+====+====+====+====+====
>>>>
>>>>Robert Campbell wrote:
>>>>
>>>>
>>>>
>>>>>Tony,
>>>>>
>>>>>I am with you. PartsExpress has transformers for about $70 which are
>>>>>affordable.
>>>>>
>>>>>
>
>
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