Is burnback and inductance the same thing?

Date 06-19-2007 16:46

No, Inductance, is a relationship of the magnetic field to the current generating it. As used in welding it has advantages in short circuit transfer for facilitating or inhibiting rapid changes in current.
Machines that came out around the 60's started placing inductance control on the faces of power sources. This has for the most part been abandoned and now the power sources are preprogramed for optimum inductance.
As it turned out it was too many bells and whistles for most welders taste.

By Kix

Date 06-19-2007 18:07

What about burnback? I thought inductance was how how far up the wire gets pinched off when it shorts out to the work. Like lets see if i can remember here, the lower you set your inductance the least amount of wire gets pinched off. The further you turn your inductance up the more wire gets pinched off. I call it the noodle knob cause it's good for getting a colder volt and amp setting to wet i better for short arc. Now about burnback, i thought it was just another name for inductance hence the burning back of the wire when it shorts out to the workpiece. Thats what i'm thinking anyway, but i can't remember. I thought most high end CC and CV come with a inductance knob on them. Now your basic millermatics and Lincoln powerMigs must just have an optimum inductance stting on them and man it's a good one.
Here's one for ya. Say on an XMT304 or any other CC CV machine WHats the arc control knob do for ya when mig welding? Does that become an inductance knob? It does something, but i don't know what. Can anyone answer that one?

By jarsanb (***)

Date 06-19-2007 18:55

Some units will have two controls, one each for burnback & inductance. The inductance control will affect the freezing cycle of the weld puddle. The more inductance introduced, the longer the weld puddle will stay fluid (arc-on) - less inductance will allow the weld to solidify faster or more rapidly (arc-off). The inductance can also be manipulated by the work lead connection (some call it ground clamp). If the cable is tightly wound on a say a spool on a welding rig, there will be a significant amount of inductance present. With higher inductance the weld will lay slightly flatter and have less defined ridge lines along the weld face. Lower inductance will promote a higher bead profile with more pronounced ridge lines. Yes the arc control is used as an inductance control on the XMT 304's. You'll probably find the the higher settings will work well with flat and horizontal fillet welds, but causes some arc sputtering when used in out-of-position applications. Not really recomended for pipe applications (5G). Turn it all the way up and weld then turn it all the way down and weld. You will definitely notice a difference. As far as the new units not having them is somewhat incorrect in my opinion. Out of the 27 units (7 different models ) I have purchased over the last 6 years all have had an inductance control mechanism. Usually a dial.

By Mwccwi

Date 06-19-2007 19:39

In the operation litrature on my welder it explains burn back like this :

Burn Back: this determines the amount of time that the current flows after the weld gun
trigger is released. Careful use of this control will reduce the amount of times the wire
end must be clipped or stubbed each day. If burn back is set too high, tip damage may
result.

Hope this helps.

By js55

Date 06-19-2007 20:16

jarsanb,
The arc control on the XMT is a volt amp curve adjustment, not inductance. Yes I know they call it that but in reality it gives the volt amp curve a little kick to increase the amperage ratio at a given operating point on the curve when it is needed, for example when oscillating cellulosic stick rods for dig and deposit. There may be some inductance variation involved since all electrical parameters will change with any change of any particular parameter (ohms law), but the primary change with the knob is the volt amp curve.

By reddoggoose (**)

Date 06-19-2007 21:06 Edited 06-19-2007 21:11

js55

The arc control on the XMT actually controls both inductance and arc force (dig). When the machine is set in the CV mode, this will control the inductance. As inductance is increased the resistance to change in current increases. This in effect will limit the number of shorts a machine can have in a given time period. Because the shorts are now limited, the amount of time the machines spends in the voltage phase increases or an increase in "arc on time" is seen. This gives an arc that looks more fluttery, and is why poor wetting materials such as stainless are ran on high inductance, it give an arc that holds the voltage on longer, helping wet out the puddle. However, too much inductance will cause your welding starts to deteriorate. Short circuit current will not be supplied fast enough and the wire will hammer the plate.

When the machine is set to CC mode such as for stick welding, then the arc force knob controls dig. As this knob is increased the available short circuit current increases. For instance when you are preset at 125 amps and dig is at 0% your short circuit current will may only reach 135 amps. When that dig is increased short circuit current will reach much higher maybe 300 amps. How high the current will reach can be determined by looking at a volt/amp curve for that particular machine.

Kix,
Burn back is the amount of power supplied for a given time after releasing the welding gun trigger. This is done to keep the end of the wire from sticking in the weld puddle at the end of the bead. To much burn back and the wire will burn back to the contact tip, not enough and it will stick in the puddle. Kix, I have heard of you out side of this forum, we have mutual aquaitances. I doubt that I live too far from you. Get hold of me offline and we should talk.

By js55

Date 06-19-2007 21:22

reddoggoose,
Thanks.
I stand corrected.

By reddoggoose (**)

Date 06-19-2007 22:18

js55,

Glad to help. When it's all said and done, the big reason we use this forum is to help each other out.

By js55

Date 06-20-2007 13:17

Its why I'm here. I'm just pizzed at myself for not finding this place sooner. I spend some time going over and printing up the voluminous stuff available in the 'archive'. This forum is a tremendous information resource.