Re: [CAD_CAM_EDM_DRO] Re: Transformer Identity - list speed

All,

Just the weight of the thing will get you a watt output close enough for
the list's uses of common AC power transformers. Some where I have a set
of tables of weight/watts for common types, post the weight and I will
look it up.

Also if the thing was powering the controls as well as the motors and
you leave the windings that were feeding the low voltage logic unused
then you can get nearly the full wattage indicated by the weight out of
the drive power windings, consistant with the wire size of the windings.

Another and maybe the best indicator if the transformer is being
overloaded is the temperature rise of the core above the room temp as
caudlet pointed out. What's that temp you say? Well its hard to say
exactly but a well made transformer can run continus duty so hot you
can't keep your hand on it.

Some types of xformers lend them selves to rewinding. If the primary is
under or seperate from the secondry and the core can be opened up
without ruining it. Figure the volts turn and how much power it can
handle to size the wire and go to it.

Mark

caudlet wrote:

>>If in your searching, you find some mathematical model for core
>
> area
>
>>vs watts, let us know.
>>
>
> The math for determinining the saturation and power handling of a
> given core size involves knowledge of the following:
>
> 1.Frequency of operation (assumed to be either 50 or 60 HZ)
> 2.Type of magnetic material and the rated saturation of that material
> in Gauss.
> 3.Cross sectional area of the core
> 4.Air gap in magnetic path.
>
> In a standard laminated core power transformer the air gap is the
> spacing between all of the laminations (not significant at 60HZ).
>
> I have used a wildly speculative rough etimate if about 10 watts per
> pound on a given 60HZ laminated core. A better indicator of output
> handling capability is to measure the circular diameter of the wires
> (not the leads) of the secondary if you can get to them. Use the
> diameter to get the circular mils (area) of the wire and look it up
> on a wire chart to get the wire size and then the max current
> capability. Derate that for losses in the closed transformer by 20%
> and you have a pretty good idea if what that winding will handle.
> Transformer designers do not typically oversize the wire inside the
> transformer since you are always playing a game as to how many layers
> of wire do I need on a certain bobbin to get the number of turns to
> get the right ratio. Even one wire size larger than needed can cause
> you to have to use a bigger bobbin to get the "fill" and that will
> cause you to have to use larger laminations and that will result is a
> bigger, heavier and more expensive transformer.
>
> If you kind of understand how a power transformer is designed you can
> reverse engineer the process by making some observations. In the end
> the best way is to measure the voltages with a true RMS meter on AC
> and then load it down with a load and measure the heat rise over
> time.
>
>
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