Author Topic: tesla coil varnish is dumb  (Read 488 times)

Offline Fumeaux

  • High Voltage Experimenter
  • **
  • Posts: 68
  • Karma: +7/-0
    • View Profile
tesla coil varnish is dumb
« on: July 14, 2019, 05:29:10 PM »
Dear High Voltage Forum!

Some time ago I started to wind a new coil. I chose a PU-dispersion paint, which turned out to be a mistake. My guess is that normal PU-paint would have worked, but the watersolvable-dispersion-stuff didn't. Now my coil has countless fingernail wide cracks. I don't think that is that big of an issue, as I have a layer of electricaltape underneath to make it structurally sound. But I'm still worried about the insulation aspect. That's why I'm asking for your thoughts on this.



Does anybody think is should fix it? And what do you suggest?

I can't reccomend this lacker.

Offline Mads Barnkob

  • Administrator
  • High Voltage Expert
  • *****
  • Posts: 1142
  • Karma: +17/-0
  • Denmark
    • View Profile
    • Kaizer Power Electronics
Re: tesla coil varnish is dumb
« Reply #1 on: July 14, 2019, 08:20:52 PM »
I tried something similar once, where I tried to fix it with a different type of varnish and that was just another mistake on a mistake. I used a oil based furniture varnish first and when that failed I tried to add spray on polyurethane and that just cracked up everywhere!

Since it cracks its either reacting with the electrical tape or you had huge temperature differences?

Fixing it.... hmm, try to fill out the cracks with another varnish type and just live with the fact that it will never be pretty :)

You have a sad doggo in the varnish.

http://www.kaizerpowerelectronics.dk - Tesla coils, high voltage, pulse power, audio and general electronics

Offline T3sl4co1l

  • High Voltage Experimenter
  • **
  • Posts: 79
  • Karma: +8/-0
    • View Profile
Re: tesla coil varnish is dumb
« Reply #2 on: July 14, 2019, 09:59:40 PM »
Huh.  What's the point of varnishing the outside, if there's air between the wires, under the tape?

I have one experience with water-based urethane; I was thoroughly underwhelmed by its performance.  It cost much more, went on much thinner (it's mostly water, so the dried film is quite thin and many coats are needed), is softer (though still strong enough not to be peeled off by fingernails alone), and seems to turn a bit gooey/sticky with prolonged contact with oils.

There probably are better-performing mixes, and I happened to get the worst one out there.  Ironically, I feel like the stuff I had, wouldn't have given you trouble -- it doesn't seem brittle enough to crack.  But then again, vinyl tape is rich with plasticizers (basically, oils that turn the plastic gooey -- pure PVC is a brittle white solid -- see where this is going?), and maybe that's strained or weakened your coating, causing it to crack.

Varnish is kind of dumb anyway, since at the voltages we're talking here, you need whole cm's of thickness to effectively insulate something.  Modest layers can still provide some protection, such as corona suppression or protecting against smaller streamers; I don't have enough experience in this direction to know how significant this is, so I'll let others fill in.

Tim

Offline Hydron

  • Administrator
  • High Voltage Engineer
  • *****
  • Posts: 265
  • Karma: +8/-0
    • View Profile
Re: tesla coil varnish is dumb
« Reply #3 on: July 14, 2019, 10:49:03 PM »
Huh.  What's the point of varnishing the outside, if there's air between the wires, under the tape?
Kizmo kinda got around this by making a pipe lathe to cut a groove for a spaced secondary winding, which both cut down the secondary impedance and also gave better insulation properties (as there were spaces between turns for varnish to fill).

I tend to agree that varnish is probably fairly futile from an electrical insulation perspective, but in terms of holding the coil together mechanically it makes sense. Especially if you have the coil on a motorised winding jig it's pretty easy to slap on some polyurethane or epoxy to hold the windings together and give some protection from minor scrapes etc.

Offline Teravolt

  • High Voltage Technician
  • ***
  • Posts: 101
  • Karma: +2/-0
    • View Profile
Re: tesla coil varnish is dumb
« Reply #4 on: August 27, 2019, 09:32:41 PM »
I just use minwax urithane in a spray can just after winding to hold the windings in place not to insulate.  the wire will strech after winding and I have had coils unravle

Offline MRMILSTAR

  • High Voltage Experimenter
  • **
  • Posts: 84
  • Karma: +3/-0
  • Cedar Rapids, Iowa
    • View Profile
Re: tesla coil varnish is dumb
« Reply #5 on: October 10, 2019, 05:26:08 AM »
Varnish is not for insulation. It is used to hold the coil windings in place during temperature extremes. If you don't varnish the coil, a big temperature swing can actually cause your secondary windings to collapse and fall off of the form. This has happened to a number of people.
« Last Edit: October 10, 2019, 08:47:56 PM by MRMILSTAR »

High Voltage Forum

Re: tesla coil varnish is dumb
« Reply #5 on: October 10, 2019, 05:26:08 AM »

 


* Recent Topics and Posts

post Re: making a useable induction forge.
[Transformer (iron core)]
rustedone
Today at 05:55:24 PM
post Re: making a useable induction forge.
[Transformer (iron core)]
rustedone
Today at 05:49:02 PM
post Re: Analog Panel Meter Shunt Calculation and Custom Scale Design
[Beginners]
klugesmith
Today at 05:36:46 PM
post Re: making a useable induction forge.
[Transformer (iron core)]
T3sl4co1l
Today at 05:07:22 PM
post making a useable induction forge.
[Transformer (iron core)]
rustedone
Today at 04:20:15 PM
post Re: 220ac to 440dc 5a boost convertor
[Voltage Multipliers]
rustedone
Today at 04:03:58 PM
post Analog Panel Meter Shunt Calculation and Custom Scale Design
[Beginners]
Mads Barnkob
Today at 07:56:20 AM
post Re: Mysterious Chinese HV capacitors
[Capacitor banks]
MRMILSTAR
Today at 05:40:55 AM
post Re: Mysterious Chinese HV capacitors
[Capacitor banks]
davekni
Today at 03:33:52 AM
post WTS [US]: pole transformer, SRSG, PTs, NSTs, capacitors, variacs, [MORE]
[Sell / Buy / Trade]
acobaugh
October 15, 2019, 09:36:55 PM
post Mysterious Chinese HV capacitors
[Capacitor banks]
MRMILSTAR
October 15, 2019, 09:12:09 PM
post Re: DRSSTC with litz-wire primary and 40 x TO247 IGBT H-Bridge
[Dual Resonant Solid State Tesla coils]
Mads Barnkob
October 15, 2019, 12:38:24 PM
post Re: How to measure voltage output of AC flyback transformer
[Transformer (ferrite core)]
davekni
October 14, 2019, 10:02:07 PM
post Re: DRSSTC with litz-wire primary and 40 x TO247 IGBT H-Bridge
[Dual Resonant Solid State Tesla coils]
Weston
October 14, 2019, 08:46:54 PM
post Re: How to measure voltage output of AC flyback transformer
[Transformer (ferrite core)]
MRMILSTAR
October 14, 2019, 08:28:19 PM
post Re: How to measure voltage output of AC flyback transformer
[Transformer (ferrite core)]
davekni
October 14, 2019, 07:27:22 PM
post Re: DRSSTC with litz-wire primary and 40 x TO247 IGBT H-Bridge
[Dual Resonant Solid State Tesla coils]
davekni
October 14, 2019, 07:01:34 PM
post Re: How to measure voltage output of AC flyback transformer
[Transformer (ferrite core)]
MRMILSTAR
October 14, 2019, 04:23:56 PM
post Re: How to measure voltage output of AC flyback transformer
[Transformer (ferrite core)]
klugesmith
October 14, 2019, 07:27:49 AM
post Re: DRSSTC with litz-wire primary and 40 x TO247 IGBT H-Bridge
[Dual Resonant Solid State Tesla coils]
T3sl4co1l
October 14, 2019, 07:10:39 AM
post Re: How to measure voltage output of AC flyback transformer
[Transformer (ferrite core)]
MRMILSTAR
October 14, 2019, 05:43:57 AM
post Re: so far video
[Spark gap Tesla coils]
davekni
October 14, 2019, 05:40:27 AM
post Re: Drsstc 4 (new direction)
[Dual Resonant Solid State Tesla coils]
davekni
October 14, 2019, 05:23:48 AM
post Re: Drsstc 4 (new direction)
[Dual Resonant Solid State Tesla coils]
oneKone
October 14, 2019, 04:37:49 AM
post Re: How to measure voltage output of AC flyback transformer
[Transformer (ferrite core)]
davekni
October 14, 2019, 03:47:03 AM
post Re: How to measure voltage output of AC flyback transformer
[Transformer (ferrite core)]
klugesmith
October 13, 2019, 11:05:25 PM
post Re: How to measure voltage output of AC flyback transformer
[Transformer (ferrite core)]
davekni
October 13, 2019, 09:29:25 PM
post Re: How to measure voltage output of AC flyback transformer
[Transformer (ferrite core)]
MRMILSTAR
October 13, 2019, 04:43:47 PM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
davekni
October 13, 2019, 07:04:20 AM
post Re: How to measure voltage output of AC flyback transformer
[Transformer (ferrite core)]
davekni
October 13, 2019, 07:00:57 AM
post Re: DRSSTC with litz-wire primary and 40 x TO247 IGBT H-Bridge
[Dual Resonant Solid State Tesla coils]
davekni
October 13, 2019, 06:36:13 AM
post Re: DRSSTC with litz-wire primary and 40 x TO247 IGBT H-Bridge
[Dual Resonant Solid State Tesla coils]
Weston
October 13, 2019, 12:41:07 AM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Hydron
October 13, 2019, 12:17:39 AM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Laci
October 12, 2019, 11:21:39 PM
post How to measure voltage output of AC flyback transformer
[Transformer (ferrite core)]
MRMILSTAR
October 12, 2019, 08:37:36 PM
post Re: DRSSTC with litz-wire primary and 40 x TO247 IGBT H-Bridge
[Dual Resonant Solid State Tesla coils]
davekni
October 12, 2019, 06:57:55 PM
post Re: so far video
[Spark gap Tesla coils]
thedoc298
October 12, 2019, 05:28:01 PM
post Re: 220ac to 440dc 5a boost convertor
[Voltage Multipliers]
rustedone
October 12, 2019, 04:58:28 PM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Netzpfuscher
October 12, 2019, 03:53:12 PM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Laci
October 12, 2019, 02:12:59 PM
post Re: 220ac to 440dc 5a boost convertor
[Voltage Multipliers]
rustedone
October 12, 2019, 10:43:48 AM
post Re: DRSSTC with litz-wire primary and 40 x TO247 IGBT H-Bridge
[Dual Resonant Solid State Tesla coils]
ScottE
October 12, 2019, 07:38:47 AM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
davekni
October 12, 2019, 06:16:12 AM
post Re: DRSSTC with litz-wire primary and 40 x TO247 IGBT H-Bridge
[Dual Resonant Solid State Tesla coils]
davekni
October 12, 2019, 05:52:51 AM
post Re: so far video
[Spark gap Tesla coils]
MRMILSTAR
October 12, 2019, 05:13:28 AM
post Re: Problems with my first DRSSTC
[Dual Resonant Solid State Tesla coils]
davekni
October 12, 2019, 04:41:19 AM
post Re: so far video
[Spark gap Tesla coils]
thedoc298
October 12, 2019, 02:58:19 AM
post Re: so far video
[Spark gap Tesla coils]
thedoc298
October 12, 2019, 02:56:17 AM
post Re: so far video
[Spark gap Tesla coils]
MRMILSTAR
October 12, 2019, 02:38:43 AM
post so far video
[Spark gap Tesla coils]
thedoc298
October 12, 2019, 12:26:44 AM

Sitemap 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30