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 Reactors and Magnetic Amplifiers Part 1.
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 Return to top of page · Post #: 1 · Written at 7:26:50 AM on 12 January 2022.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 979

Hullo All!

I have done a bit of reminiscing and started some experiments with cores and transformers.
In the Part One PDF I will send to Brad, I drag out some toroid cores and winding wire and have a play with them.
I dug out my old text books and did a bit of a refresh about mag amps and flux and stuff.

This first part is where I do all sorts of wrong things and finally do some right things and point the way forward to making a practical Lab or workshop power supply at 12 volt DC, but using magnetic amps and saturating cores. No transistors or chips allowed!
I wanted to use stuff that was available in the 1960's so modern solid state stuff is right out.

In a second part I will describe the power supply using parts you can mainly buy from Jaycar or the junk box.

Reactors, Magnetic Amplifiers and all that - Part 1


 Return to top of page · Post #: 2 · Written at 9:33:30 AM on 13 January 2022.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4602

One of the things to beware of from the era around the sixties & before is actually the winding wire. Considerable issues are to be had from the lacquer on some as it becomes brittle and fractures & peals if curved.

 Return to top of page · Post #: 3 · Written at 8:07:16 PM on 13 January 2022.
Brad's avatar
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6663

Document uploaded.

A valve a day keeps the transistor away...

 Return to top of page · Post #: 4 · Written at 8:40:13 PM on 14 January 2022.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 979

Hi Marc, interesting thing about winding wire.
When I was first apprenticed the in the 60's the winding shop used every thing from cotton covered, glass covered and laquer covered wires.
Transformers were wound with laquer and insulation between layers.
Armatures and stators had heaps of layer insulation.

Then a marvellous thing happened, winding wire suppliers introduced, if I can call them, "Poly" high grade insulation wires and advised to forget transformer layer insulation and reduce stator and rotor insulation.
That was met with disbelief by all the old hands.
The rep from Bambach wires came on site and wound a sample transformer with NO layer insulation and only primary secondary insulation.
The old guys grabbed it and flash tested it at 2 kv, test ok, no fault.
Then load test until it almost smoked no problem.

Then a rotor was wound using only interphase insulation and the wire hit in the slots with a bare hammer and slot shoe.
Flash test ok, short test ok, varnish and then load test no problem.

I was convinced and after that just scramble wound my own transformers (no more layer winding) and whacked the layers down with a hammer and and wood shoe. No failures of any music amp of mine. At work I just did the same using poly wires only, never had a failure of any transformer rotor or stator.
With the new wires and less insulation, the utilisation factor went up, I could squeeze larger wires in the slot/window and up the ratings.

I see transformers now with winding wire that the insulation bubbles if a soldering iron goes near it.....oh dear!!
Not good spec wire.

Bit of a ramble there.....I was in the middle of a revolution and did not know it.


 Return to top of page · Post #: 5 · Written at 3:54:07 PM on 15 January 2022.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 2050

I know of a real case where the wrong wire and the wrong fuse caused a house fire.

 Return to top of page · Post #: 6 · Written at 9:07:04 PM on 16 January 2022.
BringBackTheValve's Gravatar
 Location: Linton, VIC
 Member since 30 December 2016
 Member #: 2028
 Postcount: 296

Very good article Fred, quite scholarly too.

My father once said he never understood transformers until the day he realised what "saturation" really meant. The moment he understood saturation everything fell into place.

Well, now I too finally understand saturation.

Thanks mate.

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