make a transformer

[George L.]

Hello everyone,

I would like to wind my own transformer.

What could I wind the coils for the transformer around that I could find in a hardware store?

Please help,

George.

 

[stevez]

No intent to be funny - purchase a bell transformer from the hardware store, unwind it - and use the laminated core to wind your own. If all you were doing was demonstrating the principle you might wind some turns around a bolt or rod but it wouldn't be very efficient. Discarded microwave ovens have fairly large transformers that some hobbyists rewind into other voltages.

Frequency, voltage and current are significant in the selection of materials. Usually people mean 50 or 60 Hz but you might have something different in mind. Laminated iron/steel plates are common core materials as are sintered ferrite and iron powder. They do may toroidal power transformers - Amidon Associates, among others, sell toroidal cores - not sure if large enough for a power transformer.

 

[Klaus]

Hello everyone,

I would like to wind my own transformer.

What could I wind the coils for the transformer around that I could find in a hardware store?

You have to make a coil bobbin, with an inside shape that fits your transformer core exactly. They are usually made from phenolic sheeting, you could try thin fibreglass sheeting like that used in PCB boards, without the copper foil, of course. Commercial bobbins are often one piece moulded plastic, something you could salvage from an old transformer. Not found in your average hardware store.

The only useful part you *can* find in a hardware store is a lump of wood that fits into your bobbin, this requires a central hole, where a long bolt or allthread fits through, to hold the bobbin assembly to your hand drill coil winding machine. Winding a primary coil by hand is *very* tedious.

If you do use a salvaged transformer for parts, do count the number of turns of a winding ( any winding) that you *know* what voltage it produced. This gives you a turns/Volt ratio for that particular core which you can rework later for the voltages you want to wind your transformer for.

If you are thinking of high voltages you *must* use inter layer insulation, very thin mylar sheet is useful. Also, do keep the primary and secondary windings well insulated and isolated from each other, especially if you have mains voltages in one.

have fun

Klaus

 

[George L.]

here is what I am trying to do...

I need to make a step-up transformer with a 100:1 ratio. I have lots of old transformers laying around, but to take them apart you need to pry off the "E" shaped pieces of iron. After that, you can get to the bobbin, but the transformer has already been destroyed.

Is there a better way to take apart a trandformer to use it again?

Please help,

George

 

[JimB]

I have re-wound the secondaries of several transformers, and as you observe, the hard part is dismantling the core.

If the transformer has been "vacuum varnished", forget it, everything will be stuck together.

However on a transformer which has not been varnished, it is possible to remove the laminations. It is not a quick and easy job, and you may well destroy the first one or two end laminations, but with care it is possible.

Use a sharp knife to break the end lamination away from its neighbour then use a thin metal punch to tap the lamination out from the core. The use your knife to break away the second lamination and so on.
Once you have a bit of a gap in the core, the laminations should just break away by pushing the knife between them.

Take care and mind your fingers, the corners of the laminations are sharp.

JimB