• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Toroidal transformer vs induction coil (choke) confusion

MichaelaJoy

Active Member
I like dr peppers' idea of using a microwave oven transformer, although in either case you'll have to completely remove the windings and wind from scratch.

Take a look here.
https://www.ebay.com/itm/Power-Transformers-Round-Green-Toroid-Ferrite-Cores-63mmx38mmx25mm-ED-/132014640064?_trksid=p2349526.m4383.l4275.c10#viTabs_0

The good thing about this toroid is if you need two of them, you can order them, as opposed to the Velodyne
core, which would be considerably more expensive to procure.

The I.D. is 38mm (About 1.5 inches)

andybb said:
If any of you guys need woodworking advice feel free to head over to our version of your site http://lumberjocks.com/
Thank you for you kind offer. :)
 

andybb

New Member
MichaelaJoy Isn't it always the case? Just took an old microwave to the dump that had been in the shed for a year.

The ebay listing is for a ferrite core. Isn't that what is under the windings in my Velodyne toroid? It's got an OD of 4.6" , is 2.6" tall and weighs 5.5lbs. If so, stripping it and wrapping it with as many wraps of 8AWG as I can seems like the easiest solution with the least amount of guesswork regardless of the inductance. No?

One guy said, "I wrapped 8 turns of # 4 wire through an old microwave xfmr that I cut the windings out of and it still works awesome."

I know you guys hate it when a hack like me tries to do stuff that really should be done "more correctly", like when a guy on a forum wants to brush on minwax when he should be HVLP spraying conversion varnish.
 
Last edited:

MichaelaJoy

Active Member
It should be close, yes. The idea is to provide you with a source so that you don't have to rip that toroid apart.
That's a job in itself :)

Besides... where would you get the second toroid from? He stacks two of them to get more inductance, which means a cleaner DC voltage.

As far as 'hacking' things goes, my only concern is that you do not get hurt. I'm sure that everyone else here feels the same way.

I can't stress it enough. You're dealing with dangerous voltages and currents. I don't weld, so I don't know the ins and outs of welding.

But I know enough to be careful.

Please do the same. :)
 

andybb

New Member
MichaelaJoy Oh I see. Get 2 toroids for $12. The velodyne seems to be about twice as big as the ones you linked to so I may just take what that gives me, but if it is a huge chore to rip apart I might just order. I may even be able to scrounge up another old amp around the house. In the other picture (they are 2 different videos) that guy has a much smaller core more like the size of the one you linked to so using the Velodyne core seems like a happy medium between the two. I'm hoping I know enough to be careful which is why I'm using a bleed off resistor even though they don't. Done a fair bit of wiring around the house but a 200 amp rectifier & 100,000uf cap is a different ballgame and a heart stopper. I do know that. I will be careful.

Thank you very much. I won't be tearing into this until after all of my parts show up next week so any additional suggestions are welcomed.
 
Last edited:

gophert

Well-Known Member
Most Helpful Member
First, High current (>0.5 A) Toroidal cores are typically made of iron powder and lower current are made from ferrite powders. Therefore, your core is likely made of iron powder mixed with about 2wt% thermal-cure epoxy, pressed in a hydraulic press, cured in an oven then painted.

These cores magnetically saturate at their rated current (3A in your case). Any additional current is dissipated as eddie-current heating of the core. Electrical power quickly heats these cores but they cool extremely slowly. That means they can quickly exceed the rated temperature of the epoxy that holds these powdered iron structures together. Once that happens, they appear to "melt" or wilt - depends on alloy and particle size of magnetic powder used and epoxy used. These cores were rated at 70°C or less as of 1999.

Also, look at the datasheet from Toroid Corp, your transformer will 61°C with only rise 3A load. Be careful trying to get more amps out of a powdered metal core. These are not sintered ferrite ferrite is for high frequency/low current so they don't have any structural integrity after the Tg of the epoxy is exceeded.

Summary, don't use a toroidal core (as transformer or choke) if you need more than three amps - which you do for welding. If you must, make sure you only use the welder in very short bursts with plenty of down time and possibly forced air cooling.
 

gophert

Well-Known Member
Most Helpful Member
Also, here are the turns required for a 120V primary 60Hz transformer for a standard 900300 core from toroid...

Code:
Transformer size    Volts/turn
  30 VA.            0.08
 120 VA.            0.15
 500 VA.            0.35
1000 VA.            0.585
 

andybb

New Member
gophert So I should either skip the transformer part of the mod or get a ferrite core toroid? With a ferrite core of about the same size wrapped with 8AWG I should get a safe and smoother current flow or is it a lot of effort for little gain theoretically? I do have a second fan to add to the case.

Also, here are the turns required for a 120V primary 60Hz transformer for a standard 900300 core from toroid...

Code:
Transformer size    Volts/turn
  30 VA.            0.08
120 VA.            0.15
500 VA.            0.35
1000 VA.            0.585
Sorry, but that is Klingon to me without a little research as to what that means.
 
Last edited:

gophert

Well-Known Member
Most Helpful Member
gophert So I should either skip the transformer part of the mod or get a ferrite core toroid?
No, ferrite cores saturate magnetically at even lower currents than metal powder cores (even though they are not going to be damaged by the heat)..

With a ferrite core of about the same size wrapped with 8AWG I should get a safe and smoother current flow or is it a lot of effort for little gain theoretically?
There is no reason to smooth current on a stick welder. You want maximum power and pulses (even 1/1200 second peaks of power embedded in your rectified 60Hz output ) Will help you melt the steel (iron).

I do have a second fan to add to the case.
I recommend using the second fan if you feel the need to use the toroidal core.


Sorry, but that is Klingon to me without a little research as to what that means.
Not needed if you skip the core.
 

shortbus=

Well-Known Member
Using Youtube as a reference to do something is very sketchy at best. People can claim anything, like the guy saying he's an EE. You need to do more researching after finding something on Youtube.
 

andybb

New Member
Using Youtube as a reference to do something is very sketchy at best. People can claim anything, like the guy saying he's an EE. You need to do more researching after finding something on Youtube.
Good point. I thought I was doing exactly that when my ADHD OCD brain made me seek out this forum and ask questions, get specs, and post pics and schematics. :) I would definitely call this thread "more researching done on something I saw on youtube". You folks were definitely the droids I was looking for. Which is how I came to the following conclusion.......

Not needed if you skip the core.
Thank you all. Based on the research I did by coming to this thread I am skipping the inductor.choke.transformer.toroid portion of this modification. Just doesn't seem to be enough up-side for the effort involved. So, I did achieve my goal and learned a lot in the process.

Now, on to the 1.2 gigawatt Flux Capacitor! Can I use a toroid with that?
 
Last edited:

shortbus=

Well-Known Member
You don't need the ferrite core to make the choke, a short length of 1 1/2" PVC pipe will work. And this will allow you to make any size choke you want.

There is already a schematic for one on this site, just search for it.
 

unclejed613

Well-Known Member
Most Helpful Member
even my rudimentary knowledge tells me running 8AWG into an 18AWG coil is a bad idea and is above my pay grade.
you can wind the 8AWG around the same core as the existing wires without a problem. don't connect the existing wires to anything though. on the other hand, if that toroid came out of a Velodyne amplifier (usually a subwoofer), that piece of equipment is worth more dead (but complete) than the lathe is alive. Velodyne subwoofers, for instance are super expensive, and Velodyne doesn't sell repair parts, you actually have to send them the unit to have it repaired.
 

unclejed613

Well-Known Member
Most Helpful Member
if you know where you can find some scrapped CRT TVs or computer monitors, the deflection yoke (the coils on the neck of the CRT) has a rather large toroid core that with a bit of work can be removed from the yoke. most yokes are glued to the CRT with silicone compound, so they are not very difficult to remove. i've had a couple of them that were one solid piece of ferrite, but many are made of two halves with steel spring clips to hold the halves together. in some ways, the split ones can be more convenient to use because you don't have to continuously pass the wire spool through the hole.
 

andybb

New Member
You don't need the ferrite core to make the choke, a short length of 1 1/2" PVC pipe will work. And this will allow you to make any size choke you want.

There is already a schematic for one on this site, just search for it.
Now you tell me! :) Unfortunately, I searched long and hard and could find nothing referring to that.

you can wind the 8AWG around the same core as the existing wires without a problem. don't connect the existing wires to anything though. on the other hand, if that toroid came out of a Velodyne amplifier (usually a subwoofer), that piece of equipment is worth more dead (but complete) than the lathe is alive. Velodyne subwoofers, for instance are super expensive, and Velodyne doesn't sell repair parts, you actually have to send them the unit to have it repaired.
Now I'm really confused. I stripped it down last night based on previous posts then I got the impression that the core was unusable because of the material it was made from. I was wondering why I couldn't just wrap it with 8AWG but it wasn't suggested so I stripped it down. Now I have the bare core. Is it usable to wrap it with as many turns of 8AWG as I can fit on it?

The core came out of a pile of parts from 3 Velodyne amps bastardized to make one. My sub is 25 yrs old and I still love it.

if you know where you can find some scrapped CRT TVs or computer monitors, the deflection yoke (the coils on the neck of the CRT) has a rather large toroid core that with a bit of work can be removed from the yoke. most yokes are glued to the CRT with silicone compound, so they are not very difficult to remove. i've had a couple of them that were one solid piece of ferrite, but many are made of two halves with steel spring clips to hold the halves together. in some ways, the split ones can be more convenient to use because you don't have to continuously pass the wire spool through the hole.
I do have a junk large CRT.
 
Last edited:

shortbus=

Well-Known Member
Now you tell me! :) Unfortunately, I searched long and hard and could find nothing referring to that.
I was referring to the flux capacitor, not your choke. And it was a joke. :)

You said your doing the research by coming here, but when you're told doing it isn't worth what you will get as a result, you still use what some guy on youtube says. If you look at some of the otherthings he promotes on his channel you should know not to trust him.
 

andybb

New Member
Sorry again for my ignorance but you said this...
To my simple mind, I don't think you should hook up to the existing wires of the toroid. The video shows him having 2 bare toroid "forms" and winding a new one over them. I've even seen some chokes wound on a plastic core a so called 'air core'.
Was that a joke? With my limited knowledge base I sincerely thought you were giving me genuine advice, not sending me on a snipe hunt. Now I really feel stupid after spending a half hour looking for that. At my age, every half hour is valuable! :cool:

In my attempt to make a good decision I also came across a site for professional welders and apparently this mod is well known and has been used for at least 10 years with hundreds of forum posts on this subject dating to 2009 so they have practical knowledge. They were getting parts from Radio Shack! So, I am not just trusting some guy on youtube. I'm just trying to build up enough background knowledge to make an informed decision so your site has been invaluable. Thanks again. Call me crazy but I like to tinker so doing stuff like this is fun for me but may not be appropriate for a site like this.

They say stuff like...

The inductor is needed on the output, if you don't have one, it is like welding with car batteries.
I can measure the one on a small Hobart welder, but how you would measure and translate it to what you have ?
You might look for inductors added to batteries for some ideas.

_______________________________________________________________________________________

I did try the welder with and without the choke. Before I wired the choke in permanently I tried welding with it in series with the ground lead. It definitely made a difference. It reduced spatter and made for a less chaotic weld. By that I mean that things ran "smoother". I am able to create and maintain a puddle easier than without the choke. I think more inductance would be good but I was constrained by size. Could only fit so many wraps on the core. Nevertheless having what I got in there is a big improvement to not having it at all.
__________________________________________________________________________________________

Capture.JPG Tried it today. Much better than before, but found that I have to cut the wire right at the exit of the torch. This gives a short delay before the wire makes it to the workpiece, giving the cap time to charge. Otherwise, it just sticks to the workpiece and doesn't start arcing. Did a ~2.5" bead without hitting overload. A lot less sputter and better penetration.
______________________________________________________________________________________________
Re: 90A Flux-Core Welder conversion to DCEN - Redux
This is my DIY choke. 23 turns of 8AWG stranded wire THHN on a transformer core from a 1200W microwave. Measured out as 1.4mH. As I mentioned above, as a newbie welder using a bottom-of-the-line welder, I was finding it virtually impossible to do a fillet weld. After the mod my very first try at a fillet weld using 1/8" mild steel was 10X better than anything I had done before (not saying much, I know). Note that this first fillet weld passed the "sledge hammer weld test" with flying colors.​
Capture2.JPG
Capture3.JPG



_______________________________________________________________________
 
Last edited:

shortbus=

Well-Known Member
Was that a joke? With my limited knowledge base I sincerely thought you were giving me genuine advice, not sending me on a snipe hunt. Now I really feel stupid after spending a half hour looking for that. At my age, every half hour is valuable! :cool:
No the joke was about a flux capacitor. There is no such thing. An air core choke is a thing.
 

andybb

New Member
I know. I understand that now. Again, I mistakenly thought that the PVC choke (which is plastic), was one in the same as the " plastic air choke" you mentioned. You guys probably all knew that was a joke but I did not. I guess I'm just not up to speed on EE humor. Sorry for the confusion. :) Do you see anything wrong with the thinking in the above postings from the welding site forums?

Of course I know the flux capacitor is not a thing. I'm 62 years old with a post grad degree, just not in EE. That was my apparently poor attempt at EE humor. I humbly apologize for any miscommunication on my part.
 
Last edited:

shortbus=

Well-Known Member
Do you see anything wrong with the thinking in the above postings from the welding site forums?
Glad you asked that. Both of those pictures show bad welding, but not to say it was the machines fault. Some people think that wire feed, flux core or Mig are a 'magic bullet' to welding. They most certainly are not.

The one on the left is two big problems. The bad splatter is from holding the torch/stinger too far from the weld, and going to fast in the weld. The spatter is from the wire melting between the work and the torch, but the globules are still hot enoguh to stick to the work surface. Too fast a movement gives the separation between the bead that looks like clumping.

The one on the right shows less splatter but looks like it's from holding the torch a little closser to the work, but it still is being moved too fast. For a good bead to form the torch tip needs to be as close as you can get without touching. It needs to be held a consistent distance as it's moving. And speed needs to be consistent too, that picture shows the welder was changing speed as he moved, thus the 'clumping' of the deposit.

I'd be willing to bet the guy doing things the same with my Millermatic, that I paid ~$1500 for back when it was state of the art, would look like that, if he did things the same. So I don't blame the welder but the weldor in those pictures.
 

EE World Online Articles

Loading

 
Top