Re: [CAD_CAM_EDM_DRO] Re: Torroid Question

Wow ! Thanks for the "In-Depth" !
I can't believe it, but I found the Catalog I got them out of last year.
They were from All Electronics Corporation, the Winter 2001 catalog.
The ad states: 88VCT @ 4.5 amps (Series) or 44 Volts @ 9 amps (parallel)
Dual Secondaries
From the ad, these looked pretty good for driving a stepper system. I
purchased 3, just in case I need all of that juice.

If the bove is true, then CCED Member John Craddock May have guessed it
correctly ! Thanks John for the good news!

In any regard, because of the lousy paperwork, I think I will load these
as you suggest. I can come up with enough load I believe,, I have some
Calrods, and some other heating elements that might work.

If I understand what you are saying, "Heat", as well as watching wire
diameter, can reveal all I need to know.

Using common sense, like you indicate, keeping them cool enough to hold
your hand on for a while is good. But, "that funny smell in the air" is
may be bad !!

By the way, the wire diameter is .047". AND, I had an old website
bookmarked: http://www.epanorama.net/documents/wiring/wire_resistance.html
that may shed more light, of course I sure wouldn't have a clue how many
feet is wrapped up in these. I don't even know if that matters !

Thanks Bunches Guys !! I want to get started on another driver cabinet
before I find a machine to hang it on.

Chris L


caudlet wrote:

>>If I can get some bigger numbers, maybe I can use these, otherwise
>>
>>
>they are starting to look like landfill material. (Ok, recycleable
>material.....) Maybe they are 2000VA !??
>
>
>>Thanks,
>>
>>Chris L
>>
>>
>
>If you have some time Chris, you can do what we used to do with
>unmarked and military transformers.
>
> Measure the wire diameter of each winding. You will need to find a
>wire chart (type in "wire chart" in Google; use a copper wire chart)
>that will give you circular mils and cross that over to a standard
>wire gage. Using 750 circular mills per amp, calculate the suggested
>amperage. That gives you some real rough ball park numbers to start
>with. For example you can run .5 amps through a #24 wire (pretty
>small). Now hook up the transformer to full AC (use insulated
>connections). Using the secondary voltages, calculate a load
>resistance to give you the amps you want to test (R = E/I) You will
>have to have some pretty good sized load resistors to give you the
>load. You may have to get creative and use Auto headlamps in series
>or a similar type load. I actually used to use heating elements. An
>AC ammeter on either side of the transformer can be a big help, but
>you can do it all with a multimeter and ohm's law (E=I * R). Watts =
>I*E =VA. If you design up a 3A load at 44VAC the dissipated power is
>132VA(watts). At five lbs each and the size you listed I would
>expect them to be at least 100 to 150 VA units....just a guess.
>
>The objective is to run the unit long enough under load to determine
>the temperature rise of the core. Once they get too hot to hold your
>hand on for more than a few seconds, (80 deg C) it's time to crank
>the amps back. The temp will rise slowly because of the transformer
>mass and cool slowly as well. If it rises to a reasonable temp and
>stays there you are probably operating within the range of the unit.
>Your load WILL get hot and may have to be fan cooled. You may have
>to make several runs at the test using different loads to get a
>profile.
>
>The wire diameter is usually a pretty good indicator. Look at this
>way. A transformer designer wants to build the smallest most cost
>efficient transformer he can. He starts out with the required input
>voltage, input frequency (60HZ) and output voltages and the worst
>case current draw. The secondary current dictates the primary
>current which in turn dictates the size wire you have to use on
>each. Then using another formula you calculate number of turns you
>need to keep a given core area of a given core type for saturating.
>Now you calculate the "fill" of the window area for the selected
>core. Can you get all the wire on the core you selected? If not you
>have to adjust the core and recalulate the primary and secondary
>turns.
>What all of this points to is that wire diameter predicts winding
>losses and the size core you need to fit everything together. It is
>wasteful to have too large a core by making the wire size larger than
>it has to be and small wires will not carry enough current to dictate
>using a larger core to stay out of saturation.
>
>You can tell a lot about a transformer from the physical size and the
>wire diameters.
>
>Bottom line: If you burn up one of your surplus transformers below
>the current you need then its no big loss.
>
>One last note of caution. Make sure you have a piece of metal under
>the transformer to protect your bench top and fuse the primary at 2X
>the worst case predicted current draw. Make sure no voltages can
>short to the metal.
>
>
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