Three earth terminals?? a b c

crouchy · Sun May 08, 2016 3:48 am

Hi guys

I have this old machine at work that has three earth terminals on it. I normally have in plugged in to the one marked c. Have tried them all but not sure what the difference is?? Any ideas?

Poland308 · Sun May 08, 2016 7:08 am

Can you get a pic of the machine?

DLewis0289 · Sun May 08, 2016 9:03 am

I am with Poland, need to see a pic. Maybe I can learn something here. I see you are from across the pond, this may be a translation thing. Are the terminals actually labelled "earth"?

Even though we all say (including me) "ground clamp" and "ground lead" it's really not an earth ground at all in the conventional fault current bonding sense. The accurate names would be "work piece clamp" and "work piece cable" that is actually isolated from "earth" ground.

Poland308 · Sun May 08, 2016 9:39 am

I did look online and there are some picks of old Forney weld machines that appear to have 3 ground terminals. I think they were meant to be short jumpered to get you down to a lower range. Maybe? Minnesota Dave might know?

DLewis0289 · Sun May 08, 2016 10:01 am

I just Googled them also. I think Poland is correct. Just pop the cover or use a meter probably just winding taps.

crouchy · Sun May 08, 2016 12:06 pm

Here you go

Poland308 · Sun May 08, 2016 1:17 pm

Snap one of the whole front you might have lots of features depending on where you plug in at.

crouchy · Sun May 08, 2016 1:29 pm

Have to wait till I go to work tomorrow but I can tell you now there's only two switches big volts small volts. The wire is fed from a separate rover

crouchy · Mon May 09, 2016 2:32 am

Heres the full front view

noddybrian · Mon May 09, 2016 2:39 pm

Looks perfectly normal setup as most 3phase machines had prior to electronic / digital read out - they are the 3 inductance tappings - take the side off the machine & you will see they all go to a large(ish) wire wound unit that looks like a transformer.

Poland308 · Mon May 09, 2016 2:56 pm

That's what I was thinking. I bet what one you use matches what setting the switch on the left is set for.

noddybrian · Mon May 09, 2016 4:53 pm

Had'nt thought of it that way but I guess it's a starting point if you don't have any other pointers - thing with inductance settings is some machines don't weld much different when you change it - some it makes a world of difference -also it's to a degree personal preference a bit like dig on stick welders plus things like spray / short circuit / gas mix also have an effect on how the arc behaves - not sure there is a hard and fast rule - be interested if Superior has a view on this as he seems our resident go to man for heavier Mig jobs - ultimately if you keep all other variables the same I'd try it on 1 then 3 & decide how much effect it has & which way welds best - bit like non calibrated AC balance .

crouchy · Mon May 09, 2016 5:19 pm

The dial on the left and right both work together on any of the terminals, I will have a Lil play again tomorrow morning. Ive used this machine for years but never gave this much thought as to what the difference is. I have a Miller dx 220 with I much prefer

Thanks anyways guys

noddybrian · Mon May 09, 2016 5:45 pm

That's normal - coarse & fine voltage switches give the available settings ( my go to mig is a 500 amp & has 3 ranges with 7 fine settings so has 21 voltage settings total & yes it has 3 inductance tappings like yours though I've seen them fixed on some brands )- all of which go through the inductance coil last - whichever tapping you have the earth plugged in - have a play - some make little odds & tend to get left in the middle one all the time - most people like it on the higher inductance for aluminum.

Mon May 09, 2016 8:27 pm

The only machine I've worked with that had more than one ground (earth) terminal was a Lincoln CV305. The two terminals offered "low" and "high" inductance. The former was for short-circuit, the latter for spray-arc. Perhaps your "abc" setup is similar, with a midrange for globular transfer?

Steve S

DLewis0289 · Thu May 12, 2016 8:36 pm

I never thought about the inductance....makes sense. I was thinking taps. Did Henry tell you that....get it "Henry" I crack myself up. (Only myself)

The_Fixer · Fri May 13, 2016 4:07 am

You guys are right, it is Inductance.
It's purpose is (what I was taught) is to act as an electrical shock absorber to smooth out the arc in different modes. Some welders have up to 4 settings.
Generally: 1 is short arc or dip transfer
2 is spray arc
3 is flux cored or aluminium
No 3 is sometimes, but rarely, split into separate terminals

Fri May 13, 2016 8:37 pm

DLewis0289 wrote:I never thought about the inductance....makes sense. I was thinking taps. Did Henry tell you that....get it "Henry" I crack myself up. (Only myself)

Ohm My God! Did you Farad out a little milli- Henry joke from an inductance comment?

I'm resisting the urge to resonate with that comment, but I'm occillating a bit.

(I'll stop now...)

Steve S

Coldman · Fri May 13, 2016 9:19 pm

This electrician arrives home at 3am.
His wife asks him, “Wire you insulate?”
He replies, “Watt’s it to you? I’m Ohm, aren’t I?”

What kind of car does an electrician drive?
A Volts-wagon.

If you plant a light bulb in your garden, does it grow into a power plant?