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Working bit in the background, been looking at VPI the toroidal transformer, gotten a big enough pot and vacuum pump, will post some pics after awhile, just do wondering whats the best varnish to use?.
Been looking at bake off but that seems hard to get by mere mortals in this part of the world, been looking a bit at 2 comp polystyrene also a bit urethane alkyd.
Bit tempting to go with the classic boiled linseed oil or shellac.
On the other hand gotten the Madness inverter nearly soldered up with the nano invert
Murphy's friend Guru Joined: 04/10/2019 Location: AustraliaPosts: 648
Posted: 02:04pm 04 Nov 2023
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Are you planning to use this transformer in a very hostile environment?
If not I do not see the point of going to all that vacuum trouble.
Many many toroidal transformers, including 8 by myself, have been hand wound by forum members with just an epoxy coating at the wiring through the 'hole' to stop any possible humming from too loose wire turns. On mine, I tightly wrapped the outer circumference with natural fibre cord which was soaked with epoxy. Fibreglass tape could be used instead for that.
If you must use varnish, best to use the one that motor winders use. The epoxy I used was a 2:1 boating epoxy, this does no dry rock hard. 2 comp polystyrene will set rock hard and may be cracking after some time when the transformer temperature cycles.
just thought to silence the toriod a bit since humming, did first coat when laying my turns but dident really bother for the rest, wires good and wrapped with transformer cloth tape so all good there, just want to get the noise a bit
; tho no real need for it just a project i want to do, toriod run well 5-6kw here and there
Godoh Guru Joined: 26/09/2020 Location: AustraliaPosts: 458
Posted: 11:09pm 04 Nov 2023
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I used to rewind electric motors for a living. Many years ago. We just dipped the motors in a tank of varnish and waited until the bubbles stopped. Then baked them in an oven. For a transformer with not many turns, this would work fine. We never had any vacuum tanks back when I was winding motors and they all worked fine. Most failures were caused by dust, grease, water and failed bearings on the motors I worked on. Pete
Do know hot/cold dipping work well, are 3 turns x 166x1.8mm wire just hard to get the proper bake off varnish since seems nobody sells to private persons, hence why looking for alternatives. seems alkyd resins seems to fit the best bill, need to look around a bit in store Edited 2023-11-05 23:50 by Mrracerhacker
Godoh Guru Joined: 26/09/2020 Location: AustraliaPosts: 458
Posted: 08:59pm 05 Nov 2023
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An electric motor rewinder may sell you some varnish. I have wound motors and alternators with up to 16 wires in hand, all the motors I stripped out to rewind ( except the later chinese ones) had varnish all the way through the windings and slots. When we did urgent jobs we would hook the windings up to lower voltage supplies and heat the windings that way then pour 2 part expoxy over them. It seemed to run down the slots in the stator pretty well too. Not as good as dipping them in the varnish tank though. Pete
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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