Re: [CAD_CAM_EDM_DRO] Help putting together Power Supply

On Tue, 6 May 2003 07:26:46 -0500, you wrote:

>What voltage are you trying to achieve? What is your maximum current
>draw?
>
>Your transformers are center-tapped basically meaning you can configure
>them differently. The secondary voltage is determined by the voltage on
>the primary times the turns ration. The turns ratio is simply the
>number of turns on the primary as compared to number of turns on the
>secondary.
>
>You can hook your 110V between the red and black. You can actually use
>either top or bottom if you wish. You will then get 12V on the
>secondary between the blue and yellow. If you go between the blue and
>blue on the secondary, you should have 24V.
>
>It looks like these are rated for 10A on the secondary. If you hook
>them in series, you will get more voltage but you will still have to
>stay within the 10A current limit.
>

Twice the voltage, same 10 amps.

>I have never hooked two transformers in series, so I am not sure of any
>potential issues with that. I know some transformers are not completely
>isolated between the primary and secondary. Those are called
>Autotransformers, I think and you would want to make sure yours are not
>like that before hooking them in series.

They do not look like autotransformers, but despite the schematic on
the top, a quick check with the ohmmeter will figure that one out.

As far as hooking them up, first use wire nuts, and then connect the
secondaries in series. Measure the voltage across the remaining
secondary wires. If you get 24 or more volts, remove wire nuts,
solder or otherwise mark the two leads on the secondary to be
connected together. Otherwise, reverse one, but not both, of the
secondary leads. You should then get 24 volts.

If your capacitors and rectifiers will stand it, better to have one
rectifier bridge and one set of capacitors, you don't need two unless
you have a need for two isolated supplies of 12 volts or so each.

Harvey

>
>Also, dealing with AC, you can't simply add the voltages as you need to
>take into consideration phase relationship. Might be better to do that
>after the filtering and regulation.



>
>Jon
>
>-----Original Message-----
>From: logiccooling [mailto:logiccooling@...]
>Sent: Monday, May 05, 2003 9:38 PM
>To: CAD_CAM_EDM_DRO@yahoogroups.com
>Subject: [CAD_CAM_EDM_DRO] Help putting together Power Supply
>
>I bought all the stuff I need to build my own PS and I think I
>understand most of it, but I'm a little unsure about how to hook up
>my transformer(s). I bought 2 of these transformers:
>
>http://www.logiccooling.com/images/xform.jpg
>
>I wasn't expecting there to be 3 wires on each side. I want to run
>110V, not 220V. Should I just use the 110V and the common on one
>side, and the corresponding 12V and common on the output side?
>
>Also, I've got 2 of each part (xformer, rectifier, 27,000 uF caps).
>Would it be better to wire 2 completely different power supplies and
>then run their outputs in series to get the desired voltage? Or
>should I wire the Xformers together internally for the higher voltage?
>
>
>
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