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Is it possible to use ZVS as a welding gun?

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steven968

Fri Jan 07 2011, 03:50AM

Registered Member #3516 Joined: Wed Dec 15 2010, 10:40AM
Location: Australia
Posts: 32

As the title shows, the arcs from flyback can generate huge amount of heat, so I reckon if it can be use as a welding machine?:-p

rp181

Fri Jan 07 2011, 04:43AM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
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Posts: 1529

Welders typically use low voltage at high currents. For example, when I am MIG welding moderate steel of a medium thickness, I use 19.1 volts. A arc is started by contact, and is maintained by current flow.

Arc welders are usually 20-50v, and sometimes have a high voltage starter to initiate the arc.

Adam Munich

Fri Jan 07 2011, 05:42AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Sure you can! Use a couple high amperage IGBTs or mosfets and a strong capacitor. Use a big ferrite core and put 6+6 turns on it as a primary, then put a 15 turn secondary on it.

rectify that output with a big schottky diode bridge and then feed the whole thing with a bank of car batteries or a couple re-wound MOTs.

Arcstarter

Fri Jan 07 2011, 05:58AM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Grenadier wrote ...

Sure you can! Use a couple high amperage IGBTs or mosfets and a strong capacitor. Use a big ferrite core and put 6+6 turns on it as a primary, then put a 15 turn secondary on it.

rectify that output with a big schottky diode bridge and then feed the whole thing with a bank of car batteries or a couple re-wound MOTs.

What is flyback about doing that? If you wound powerful enough MOTs to power something strong enough to weld, just soon use the MOTs in the first place.

Adam Munich

Fri Jan 07 2011, 06:10AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Idk, he asked for a ZVS...

steven968

Fri Jan 07 2011, 11:29AM

Registered Member #3516 Joined: Wed Dec 15 2010, 10:40AM
Location: Australia
Posts: 32

why low voltage is applicable?

radhoo

Fri Jan 07 2011, 01:15PM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701

To clarify, you shouldn't use a high voltage to generate a hot arc, because it lacks precision, not to mention damage on components you want to solder.
On the other hand the correct approach is to generate a very low voltage (eg. 2V) but at a few amps, and use it to heat a tick piece of wire. We had such "soldering guns" , using a 100W transformer instead of the ZVS inverter approach you mentioned. They look like this:

The high current heats the the soldering tip, made of a loop of copper wire.

Using ZVS things are easy. Build a royer oscillator and use a small ferrite core (you don't need a lot of power), with a 5+5 primary, and a few turns tick wire secondary. No rectification needed, simply short-circuit the secondary with a loop of thinner cooper wire.

Here's something similar that I built, to give you an idea:

It is a high current ZVS inverter. Replace the TV Flyback with a custom made secondary of just a few turns.

This would be called : Inverter based soldering station

LE: I read soldering instead of welding , sorry.

Fabio

Sat Jan 08 2011, 08:32PM

Registered Member #122 Joined: Fri Feb 10 2006, 12:55PM
Location: Milano Italy
Posts: 148

Yes, you can, and the overall results are better with the ZVS than an ordinary arc welder!

I tried once few years ago using this royer:

To operate it i used just the rectified mains (controlled with a big variac), as secondary i used 8 turns of 25 squared millimeters cable suspended about 5 centimeter over the primary coil (the welding current can be controlled by varying the distance between the coils)...... the open circuit voltage was 380V RMS at 15 kHz and the optimum welding current was set on 80 amps
this system is quite bulky and expensive respect to an ordinary stick welder but it have the great advantage that the arc is really easy to start and almost impossible to incidentally extinguish;
in addition, since scratching the electrode over the piece is not required to start the arc, the electrode is also difficoult to stick.

anyhow, building an inverter based arc welder from scratch can be much expensive than buying one so i didn't suggest the self made version unless you have plenty of free IGBTs, power capacitors, diodes, heatsinks, coils and many more high power components.

PS: i always use an ordinary cheap magnetic AC-only arc welder followed by an external electromechanical HF arcstarter, seems a good solution for normal welds and the overall results are OK..... i suggest the use of an HF arcstarter to everyone, is a really big help!

ubuntupokemoninc

Sat Jan 08 2011, 11:01PM

Banned on 1/22/2011 for repeated rule violations after multiple warnings.
Registered Member #3299 Joined: Sat Oct 09 2010, 08:11PM
Location: Bantown, USA
Posts: 220

as matt said why use a zvs just put a couple of rewound mots in series, now you have a welder.

Fabio

Sat Jan 08 2011, 11:28PM

Registered Member #122 Joined: Fri Feb 10 2006, 12:55PM
Location: Milano Italy
Posts: 148

if you need an arc welder (not an arc making machine) you need some kind of current stabilizing/limiting system.
in a common welder the current stabilizer is made with a variable magnetic shunt and it should be set properly accordingly to the thickness of the piece and the size of the electrode, if you use a MOT you can have no more than one fixed ballast so the output current can be higher or lower than required causing a bad weld

in addition, a MOT is outrageous small for his rated power, if you use it as a welder it won't last longer (even if you use 2 or more).

A classical (magnetic) welder is dirt cheap and have the required current stabilizer, if you want a better performances and you want homebuild something, you may add an HF arcstarter (even if many modern inverter welders have this function and they start to become cheaper)

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