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Registered Member #610
Joined: Wed Mar 28 2007, 09:44PM
Location: Middletown, RI
Posts: 110
Thermal paper? or electrical insulation paper?
Ahh, nevermind. I'm sure they use the paper to protect layers of windings from each other from their increasing voltages. I suppose it would be safe to use it, but that must depend on the copper's insulation material (which probably increased in break-down-voltage since 1980, about the time the E-I core was made).
I am beginning to remember that there is just as much art involved with electronics as there is science.
Registered Member #75
Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711
It is about the size of a MOT, so I would guess it comes out in the 1kW range. Input voltage is totally irrelevant though, even if you gave it a 1V 1kA primary it would not change the power.
Registered Member #610
Joined: Wed Mar 28 2007, 09:44PM
Location: Middletown, RI
Posts: 110
I do not have an o-scope anymore (though I should really buy one). I'm trying Steve Connor's idea... This is what I have so far, and it starts to buzz to the point where I have to talk loudly for someone to hear me when it draws about 1A with the primary at 50V. The primary has about 100 turns. I am assuming that the core is way beyond the saturation point when this is happening? I suppose the sure-fire way is to check the waveform of the magnetizing current.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
If you make a quick graph of current (voltage across the series resistor) for the X-axis and primary voltage for the Y-axis you will create a B-H curve for your transformer.
You will see on the graph where the core becomes non-linear.
Registered Member #105
Joined: Thu Feb 09 2006, 08:54PM
Location:
Posts: 408
Just saw this thread while I was designing my transformer, and thought i might as well revive this one instead of starting my own. I have a core and bobbin all separated, and have just ordered some 20AWG wire for the primary. The core is suitable for about 150VA, and for a 500VCT transformer, I have chosen 26AWG wire for the secondary. The secondary before was a 24V secondary, with 49 turns (2.04 turns per volt). However the primary was 263 turns for 117V (2.25 turns per volt) From this, I have decided on winding 520 turns for each half of the secondary. My question is, with new magnet wire, do I need to include insulation between layers? There should be a very low voltage between layers (15 layers) with my bobbin size. Also, would a scramble winding be okay for this voltage difference between turns, or would a layered secondary be worth the additional trouble? If i scramble wound the transformer, I would still be sure to go across the bobbin in an even manner, just not having to worry too much about crossed wires.
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Making a 60Hz power transformer using existing laminated E core
