Inductor value for a mig welder

Well, it's more like this: on a stick welder, the resistance of the arc varies with the arc length. Since it's desirable to put the same amount of heat into the pool for each inch of weld, it's desirable to flow a constant current despite the change in load resistance. Thus the attempt to make the DC source look inductive - an inductor strongly resists changes in current.

GWE

My big old New Zealand made (in 1975)EMF Lynxpak 200A MIG has an inductor. It is on a variable slide, so you can dial in the amount of inductance to adjust the arc characteristics. I don't know the value of it, but it is around 100mm diameter and 350mm long. Geoff

True enough but the constant current is really achieved through the shunts in the transformer. Lots of stick welders don't even have an inductor.

billh

which is desirable in short circuit mode- Google induction short circuit welding- my MIG welder at work has a 4 position inductance control

I'd say the LC was an 1/root(LC) time machine. Might be the high voltage stick arc to start stuff a bit easier, or keep it going.

The inductor and cap do nothing during pure dc steady state - the current stabilizes in the coil and the voltage across the cap remains the same. Steady state (unknown in welding):-)

The step response and when arcing on a plate to start current is where the LC comes into play - The two reactive elements produce sharp (more or less) edges - spikes that jump through oil or film and clothing... and starts the current flowing due to ionization. Once flowing, the coil has constant current and idles to standby. The cap is trying to hold the output voltage the same - just like a steady hand. But once welding - the cap is swamped - lower impedance in the arc than across the cap.

So it seems that they only work when one strikes an arc or re-strikes or runs into some scale or something that alters the current. Agree with an long time friend - GWE Martin

Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder

billh wrote:

Hello Geoff, A picture would be great but too much to ask of you, but, so that I can form a mental picture:

How many turns of wire?

Is it a single layer of wire?

How far in and out does the variable slide travel? I imagine all the way in and perhaps half out.

What is the slide made of? I am imagining laminations in a squarish block

How is the block held mechanically?

How do you adjust the inductor setting in actual practice?

Do you find there a sweet spot in the inductor setting for a particular thickness of metal being welded or just a vague feeling that the setting is correct?

Sorry for so many questions, just interested. Regards, John Crighton Sydney

Your first mistake was were you bought it at H.F.

Yea Tony your right, however i put it aside and the short warranty went out before i really tried using it. I was trying to salvage it for something? i thought of using it for a low power arc welder but the open circut voltage is only 30VDC & from what ive read rods require twice that to start a arc, I have determined the inductor didnt help, the problem was the wire feed motors voltage comes off the welders output & varies as the unit welds, so now ive got to build a regulated / adjustable wire feed voltage supply and try again. I thought the price was to cheap to be true but found out it wasent cheap at all.

CV welders tries to maintain constant voltage while welding in a finely tuned way. Inductance is part of this fine tuning.

Some wire feed welders have a slope control which changes inductance. The slope control adjusts current flowing when elctrode is shorted to work. Increasing inductance in series with work increases slope retarding rapid arc current changes and limiting maximum short circuit current, reducing spatter. More slope is needed for short circuit transfer and little slope is used for other transfer modes. Most modern MIG welders don't have slope adjustment.

In short circuit transfer the wire shorts to work 20 to 200+ times a second. Short Circuit period: Wire shorting to work causes amps to increase rapidly. Voltage drops from arc voltage to much lower level aswire shorts to work and arc goes out. Amp current increase as volts rise as CV power supply trys to maintain voltage . Wire continues to feed into puddle forming a cone until molten wire feeding into puddle is pinched off and arc reignites. Arc Period: Amps begins to fall off while voltage rises sharply. Arc heats wire and puddle causing cone to flatten into weld puddle and ball of molten metal to form on end of wire. Wire is feeding while ball forms and brings ball into contact with puddle causing electrical short circuit starting another cycle.

If molten metal ball 2 to 4 times wire size drops from wire end before wire shorts to work it is Globular transfer.

If large moten metal ball 2 to 4 times wire diameter shorts to work it will explode causing lots of spatter.

Volt and amp meters don't show these quick volt/amp changes only indicate average voltage or amperage.

replying to Andy Dingley, Kenneth E. Ghost wrote: Easy to add argon to the HF 90 amp. I am in the process as I speak. Fun too, learning a lot. Added a bridge R , 160,000 mf cap total, torrid coil, single 20 amp outlet in front panel/power on indicator , heavy power cord and very heavy work clamp. works like a dream and, its 120 v 20 amp rated, I can take it anywhere. Gas hookup will be done this week.

replying to Ignoramus29795, TimofGlazz wrote: They do not call it a mig, they call it a flux core.

replying to Grant Erwin, TimofGlazz wrote: Easy there buddy, hold your fingers back from that key board and open up a new tab to do some research before you make yourself look like a gorg-ass. And if you make gorg-ass beads all day yourself. Well then good for you, you know how to flip a switch and close a circuit and not kill yourself doing it. I bet those welding fumes don't take any crud from you because you're tougher then them.

replying to Ignoramus29795, TimofGlazz wrote: They do not call it a mig, they call it a flux core.

replying to Grant Erwin, TimofGlazz wrote: Easy there buddy, hold your fingers back from that key board and open up a new tab to do some research before you make yourself look like a gorg-ass. And if you make gorg-ass beads all day yourself. Well then good for you, you know how to flip a switch and close a circuit and not kill yourself doing it. I bet those welding fumes don't take any crud from you because you're tougher then them.