High voltage transformers, salvage value?

I doubt it. Many transformers are potted in varnish, and when you unwind them, some of the wire insulation peels off, leaving bare spots. If you find some oil immersed ones, you may have more luck disassembling them. I have reused laminated core materials, but I always use new wire.

Chris Jones wrote: (snip)

PCB's are pretty nasty in lots of biochemical ways, but flammability is not one of their problems, if I recall correctly. In effect, the oil they are made with has already been burnt in chlorine (well, reacted with, anyway) so that the carbon content no longer has much interest in oxygen. Some of the trade names for PCB transformer oil was No-flamol, Saf-T-Kuhl, and Inerteen. Some PCB filled devices were just labeled with the assuring claim, "Non-Flammable Liquid".

I have some high voltage transformers, for 10-15 kV. Unfortunately, they are made for 400 Hz, so, I assume, they are not usable for 60 Hz.

Still, I wonder if perhaps I can salvage wire with HV insulation from them. I do not know what is inside them since they are in sealed steel cases. These are military (navy) items.

Since I have a Franceformer, which I could use for some HV fun, I wonder if I can reuse some HV wires from the military transformers.

Tesla coil builders might be interested. What is the VA rating?

Regards,

Boris Mohar

Got Knock? - see: Viatrack Printed Circuit Designs (among other things)

void _-void-_ in the obvious place

So, let me go back to my another original question. Are there wires with HV insulation, that I could take out and reuse. Thanks

Probably once you have removed it, the wire will no longer have HV insulation. It might have a coating of cancer-causing polychlorinated biphenol (sp?) oil though, assuming it is an oil-filled transformer. I've heard you can identify those oils in their pure form by the characteristic that they are heavier than water, however I have never wanted to get close enough to the stuff to be able to test this, and I don't recommend that you do either. If it is an oil-filled transformer, look for some text on the rating plate that says "No PCBs". If you don't see such a label, then be very careful, especially since the photos on your website show kids in your workshop.

By the way, if you connect the primary coil to a 12V battery and then disconnect it, you should be able to get a nice spark across the secondary terminals. It might well jump up to a 1 inch gap (mine did), though I'd start with a 1/8 inch gap to see if it will jump that first. It is possibly somewhat dangerous, so don't allow the spark to zap a human, and note that you can also get a nasty zap from the primary which is educational as to the nature of energy storage in inductors, but unnecessarily painful. Don't leave the primary connected to the battery for more than 1 second at a time since it could heat up fast. If your transformer really does have PCBs in it then don't even do this experiment at all, since a PCB fire would be horrible.

Chris

If you have a use for an HV transformer, then maybe it's worth feeding them with 400Hz to make use of them.

Michael

Well, what's the easiest way to make 400 Hz?

They are in boxes in my garage, but I would say perhaps 400 watts. I will double check if you think it can help you arrive at some reasoned opinion.

"Ignoramus4939" skrev i en meddelelse news:FCU9f.16341$ snipped-for-privacy@fe28.usenetserver.com...

How long is a piece of string??

For what power, what input voltage, does it need to be compact, do you want one or many, do you care about efficiency, price, volume, weight, noise, purpose ..... e.t.c. e.t.c. ????

I am partial to single-ended resonant SCR converters myself for high voltage - because these are really simple to build and SCR's can handle lots of power for very little money. IGBT's and MOSFET'S work too.

I'm guessing:

Tim

-- Deep Fryer: a very philosophical monk. Website:

Thank you, Chris, John, and others. The transformers that I have are quite wimpy, 0.0005 A only. At least the ones that I checked last night. I will cut off and keep whatever tiny amount of HV wires on the outside and will throw the rest to garbage.

Now, that was a good guess.

lots

Don't suppose someone could suppply a link to a design of one of these??

Fair enough. I just guessed that any gases that did come out when they get hot would probably not be good for you.

Chris

I read in sci.electronics.design that Chris Jones wrote (in ) about 'High voltage transformers, salvage value?', on Thu, 3 Nov 2005:

Which is true - dioxins are produced. Very nasty indeed. PCBs can be destroyed very well by incineration above 1200 C. But incinerator operators won't run them that hot, because the lining erodes too quickly. At 800 C, wall-to-wall dioxins.

I placed a copy of the entire patent on abse.

I *did* check but, sadly, all of the good papers are now sealed solidly within the $$$ IEEE and Inspec databases (in the good old days, real papers could often be retrieved in CiteSeer and via IBM's patentsearch ...).

You *can* buy articles with the olde credit card - the problem is that many articles are written mostly because the author needs to publish rather than to divulge information (i.e. they are crap) and you do not see that before it is too late.

Maybe here:

The "switching power supply design" book by Pressmann;

and Kjeld Thorborg (my old examiner) "power electronics";

are some of the best sources and they contain references to classic papers. if you are at school/university/work they might have a subscription to IEEE and Inspec.

The Library is a good place considering the price of Thorborgs book.