Mag wire

[killivolt]

Ok, so I got another transformer rapped and I don't want to heat up the wire to burn off the Varnish.

I thought ok before I solder the wires to the pins, I can scrape the wires with a razor or sandpaper.

But what about finger nail polish remover or Lacquer thinner?

How do you do it?

kv

 

[alec_t]

How do you do it?

I burn the varnish (match or lighter or gas jet) then gently sandpaper.

 

[ronsimpson]

I just heat up the wire. Don't do that for 10 minutes but solder and then get off the wire. You can practice on some wire. The insulation should only burn off at the solder joint. If the iron temperature is set just above the burn point the wire inside the transformer will be fine. I have done this many times.

The wire between the solder pin and the tape might be a little questionable so don't let the wires cross 0.1 inch away from the pin.

If you wind you transformer correctly there will not be many volts across the insulation. Normally there might only be 2 volts per turn. From one turn to another the voltage is very low. I often tape between layers but you don't have to. If there are four layers then the voltage between layers is a fraction of the total voltage. Don't let the starting wire and ending wire cross when using high voltage windings. (no problem at 10 volts) I often have 800 volts across a winding.

If you need primary to secondary isolation; then use tape not wire insulation. UL, VDE and CSA do no count wire insulation.

Solder Ease Wire is made to hand solder. (or solder pot)

 

[killivolt]

I just heat up the wire. Don't do that for 10 minutes but solder and then get off the wire. You can practice on some wire. The insulation should only burn off at the solder joint. If the iron temperature is set just above the burn point the wire inside the transformer will be fine. I have done this many times.

The wire between the solder pin and the tape might be a little questionable so don't let the wires cross 0.1 inch away from the pin.

If you wind you transformer correctly there will not be many volts across the insulation. Normally there might only be 2 volts per turn. From one turn to another the voltage is very low. I often tape between layers but you don't have to. If there are four layers then the voltage between layers is a fraction of the total voltage. Don't let the starting wire and ending wire cross when using high voltage windings. (no problem at 10 volts) I often have 800 volts across a winding.

If you need primary to secondary isolation; then use tape not wire insulation. UL, VDE and CSA do no count wire insulation.

Solder Ease Wire is made to hand solder. (or solder pot)

Here's a pic.

 

[jpanhalt]

Finger nail polish, lacquer thinner, even "aircraft" paint remover won't work. Assuming you are using magnet wire that is not solderable, I would use either scrapping or a molten salt bath (KOH or NaOH). A little NaNO3 (10% to 20%, not critical) added helps enormously. The reaction is quick and the wires come out bright copper.

Here's a picture of my hot pot:


John

 

[killivolt]

Here's a finished photo, I used emery cloth work quite well.

 

[killivolt]

Finger nail polish, lacquer thinner, even "aircraft" paint remover won't work. Assuming you are using magnet wire that is not solderable, I would use either scrapping or a molten salt bath (KOH or NaOH). A little NaNO3 (10% to 20%, not critical) added helps enormously. The reaction is quick and the wires come out bright copper.

Here's a picture of my hot pot:

View attachment 80839
John

I tried the both, it didn't work, as you can see I used emery. I'll give the other a go, next time.

Thanks, John.

kv

 

[KeepItSimpleStupid]

I wound my first toroid back in 1970's, Just recently I wound two toroids.

Remember, that when you wind them, you take the wire and essentially fold it in half. Wind one half and ten the lother, so you don't have to pull all of the wire through the core. The max is 1/2. Mine was a bifilar, two different wire guages and about 80" long. I wound about 80 turns in about 25 minutes.

Yours looks good though, You should keep the windings evenly spaced along the entire core.

I had troubles with the calculations that I needed, so I did use the trial and error method. A BIG PROBLEM is that the core constant can vary by +-30%. That's probably by batch. So, a commercial winder, could wind one, test and then wind the rest assuming the cores came from the same batch.

I tried to do some calculations to figure out how long the wire would have to be for x number of turns and I initially estimated the windings to be square which results in a lower estimate.

If your winding a large core or using finer wires, you can make a tool that can help you wind. This is essentially a flat bar with a small cutout except for the two ends. You wind onto the bar, then pass the bar through the core.

Formvar is very nasty to strip. Razor blade scraping or use a Dremel and a sanding disc or grinding disc.

 

[ronsimpson]

KilliVolt, Your transformer looks good. You have 1/4 inch of wire between the solder job and where the wires touch. The wire will cool in 1/10 of a inch. In production we wind the wire on the pins and put it in the solder pot. Solder all the pins on one side at a time.

 

[jpanhalt]

@KISS,

I used a shuttle/bobbin , like is used for weaving, for the few toroids I have wound that required a lot of wire. They required 300 to 400 turns. For just a few turns of heavy wire, I lay it out on the floor and feed it through winding from one direction or both, as you describe. I try to avoid unnecessary bends that cause work hardening of the copper and keep it from laying nice and flat..

John

 

[ronsimpson]

The shuttle-bobbin is good. If you watch the machines work they have a round bobbin with a break in it. The bobbin is like a "C". You put the empty bobbin around one part of the core. Then spin the bobbin and spool 10 feet of wire on the bobbin. Cut the wire. Now spin the bobbin and it winds the wire around the core. Now remove the empty bobbin.

Words don't work I need to make a video.

 

[jpanhalt]

Words don't work I need to make a video.

You are right. I reviewed the patents on automated winders. I was only making a few ignition coils for model aircraft. If I had to make more, I would probably have copied one of the patents. It is quite hard to get the same, consistent wire density/tension when winding by hand as a machine gets.

John

 

[RODALCO]

I use sandpaper . a small file, or a sharp knife to scrape off the varnish.

 

[killivolt]

I wound my first toroid back in 1970's, Just recently I wound two toroids.

Remember, that when you wind them, you take the wire and essentially fold it in half. Wind one half and ten the lother, so you don't have to pull all of the wire through the core. The max is 1/2. Mine was a bifilar, two different wire guages and about 80" long. I wound about 80 turns in about 25 minutes.

If your winding a large core or using finer wires, you can make a tool that can help you wind. This is essentially a flat bar with a small cutout except for the two ends. You wind onto the bar, then pass the bar through the core.

:WINK:

Alway's good.

Thanks,
kv

Edit: Thank you for all your responses. I learned so much. Thank you, Thank you.

 

[killivolt]

The shuttle-bobbin is good. If you watch the machines work they have a round bobbin with a break in it. The bobbin is like a "C". You put the empty bobbin around one part of the core. Then spin the bobbin and spool 10 feet of wire on the bobbin. Cut the wire. Now spin the bobbin and it winds the wire around the core. Now remove the empty bobbin.

Words don't work I need to make a video.

I can visualise it.

Thanks, Ron.

kv

Edit: My "Mom" or to our friends across the pond "Mum"
She (Lovingly), was a very good (Seamstress) She could weave out a " Cigaret burn" in a mans "Evening Jacket" and to watch it as a child, was simply amazing.

 

[killivolt]

The shuttle-bobbin is good. If you watch the machines work they have a round bobbin with a break in it. The bobbin is like a "C". You put the empty bobbin around one part of the core. Then spin the bobbin and spool 10 feet of wire on the bobbin. Cut the wire. Now spin the bobbin and it winds the wire around the core. Now remove the empty bobbin.

Words don't work I need to make a video.

Wait, still make the (Video) Please!!!!!!!!!!!!!!!!!!!!!

 

[ronsimpson]

Wait, still make the (Video) Please!!!!!!!!!!!!!!!!!!!!!

video:

The bobbin is the large metal circle. It is placed around the core then filled with wire first.

This is faster than by hand.

Very good video. Shows the loading of the bobbin and then the winding.

Home made example. will not work on small cores.

 

[rumpfy]

Magnet wire enamel varies according to the application.
The traditional material was Poly Vinyl Acetate and was stable to soldering heat, making it necessary to scrape it off for soldering.
A later material was Polyurethane which is unstable to heat but good enough for many applications where the temperature rise is not great;eg. small coupling transformers,HF coils, etc.. It is used extensively in appliance products because of its ease of tinning/soldering.

For really high temperature work, polyester materials are used. eg power transformer for say steam generators. Needless to say, the development of new solderable AND high temperature, materials continues.
Mostly for what we do here, polyurethanes are good enough.

 

[jpanhalt]

The traditional material was Poly Vinyl Acetate and was stable to soldering heat, making it necessary to scrape it off for soldering.

You probably mean "acetal" (Formvar). Acetal is: RHC(OR)2. You might say it looks like two ether linkages on a single carbon. It is derived from an aldehyde. Acetate is an ester: RCOOR.

Here is a listing of some common insulations from Essex with temperature ranges: **broken link removed**



Edit: Here's a little more information on Formvar. Apparently it is a co-polymer with the ester (acetate), but common usage seems to prefer calling it an acetal: **broken link removed**

John

 

[steveB]

Yes, there are so many different coatings. Some can be removed with heat and some with chemicals. But, there is one type that is almost impossible to remove except by mechanical means.

When I use this type of wire, I use a serrated knife with round serrations with diameter matched to the diameter of the wire. It's hit or miss whether you can find a knife that matches the gauge of your wire, but if you do find it, then scrapping can remove the varnish without damaging the wire too much. Alternatively, you can dismantle a gauged wire stripper and use one side with the half circles for the proper gauge wire. Again, scrapping (must use the correct attack angle) can strip the coating without damaging the wire too much.

You can also use a round jewelers file, of the correct diameter, to cut a half circle into a knife. A 15-30 degree sharpening angle will make a nice sharp edge that can be resharpened as needed.

Any of these tools require practice so that you scrape with the wire between the blade and your thumb at the correct angle without cutting yourself and without nicking the wire.