Designing transformers

Well, but it was on the other side of the "iron curtain" that time. Tesla sold similar kits here, but there was no winding on the former. If one managed to get the proper wires AND had access to a winding machine (some hamradio clubs owned one), he could make an almost professional transformer. IF...

VBR from Ivan

I found a picture of the original DIY transformer kit I mentioned.
They were sold by Amroh, a well know component seller at the time:



This is more or less what you would get:

Hi all,
I hate winding power transformers, too. It was nearly impossible for a ham to buy copper enameled wires in the 70s and 80s. They were distributed on huge drums to factories only. If some surplus wires appeared in a hobby shop, one could not select the diameter he needed. The common way was re-using old wires, having a hope it would not short-circuit.
Old transformers, chokes and motors appear rarely in garbage bins in Czechia. Some people make their money disassembling these things and selling copper for scrap. Metal recycling is good, but they often destroy otherwise usable items.
Winding more than 100 turns without a winding machine is a real nightmare. Even using the machine, when a 0,07 mm dia wire gets ripped for the third time on the same coil, I go mad. So I have always preferred using factory made power transformers and adapting the circuit to the voltages available.

VBR from Ivan

Hi Ruud,
I seem to remember something about those being sold by some of the "emporiums", but in the 70's I was working abroad a lot (in the military). Also, money was a bit tight. You can still buy them with the primary ready-wound. Have a look at:

https://www.fabian.com.mt/en/products/webshop/16842/transformer-kit-system-100va.htm


I always re-wound my own transformers from transformers that I found in the rubbish bins. It is surprising what people throw away.

My favourite is the Christmas-tree lights. The larger ones with 100+ tungsten lamps are usually about 25 Watts, or so, and even though they are all from different manufacturers, they nearly all use the same size iron stampings. That means I can use as many stampings as I like, for example twice the number, and get a 100-Watt transformer.

In Spain I got those really cheap "battery eliminators" for just a couple of Euros (brand new), but the windings are low quality.

I love winding transformers, the actual winding itself is like watching paint dry, but it does go very fast. It also gives me the inventive opportunity to use the 3D printer for winding-aids.

But I agree with you, if it is all done the old-fashioned way then it can be very boring.

Best regards from Harry

I just read your article about 'designing transformers'.
I remember that in the 70's, there were DIY transformer kits.
They consisted of a coil former with the ready wound primary winding for the mains voltage (we had 220 volts here at the time), and the E and I laminations. The only thing you had to do, was to wind the secundary winding(s), so usually not very many turns. (Except if you were a 'tube man'...)
An indication of the number of turns per volt was included. You had to find the wire for the secundary winding(s) yourself.
The transformer kits were available for different VA values.
At the time, this was a great option if you needed a 'special' transformer, or a transformer with a non-standard output voltage.
It is really a pity that they are no longer available (it seems), because I HATE winding transformers!