Type of welder?

"amdx" wrote: (clip) It has a slider that (from the outside) seems to move into or out of a core. Does anyone have more info regarding how the adjustment varies the output? (clip) ^^^^^^^^^^^^^^^^ If it works like my welder, the core is laminated iron. The farther you insert it into the coil, the more inductance you introduce, which, of course, lowers the current.

So would the core be moving into an inductor on the primary of the transformer? Or the secondary? Mike

You are used to fixed core transformers. Standard fair.
This is a variable core - you push the core in and out - allowing more or less coupling between the two coils.
The amount of core also determines the power ability and since this is used as an approximate setting - the physics can be complex indeed.
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net TSRA, Life; NRA LOH & Endowment Member, Golden Eagle, Patriot"s Medal. NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member.
amdx wrote:

Thanks Martin, Darn, now I'll have to open it up to see the variable core transformer. Mike
> You are used to fixed core transformers. Standard fair. > > This is a variable core - you push the core in and out - allowing > more or less coupling between the two coils. > > The amount of core also determines the power ability and since this is > used as an approximate setting - the physics can be complex indeed. > > Martin > > Martin H. Eastburn > @ home at Lions' Lair with our computer lionslair at consolidated dot net > TSRA, Life; NRA LOH & Endowment Member, Golden Eagle, Patriot"s Medal. > NRA Second Amendment Task Force Charter Founder > IHMSA and NRA Metallic Silhouette maker & member. > > > > amdx wrote: >> Hi All, >> I just bought a used Sears Craftsman 113.201371 Welder. >> I'm curious about the current adjustment, it doesn't have >> a tapped transformer. It has a slider that (from the outside) >> seems to move into or out of a core. >> Does anyone have more info regarding how the adjustment >> varies the output? I understand tranformers and inductors, >> just trying to end my curiousity before I open it up to see >> how it works. >> Thanks, >> Mike >> >> Just learning to start an arc! > >

All of the moveable shunt welders are based on the maninpulation of the flux density. In order for an amp to be generated in the secondary, a certain number of magnetic flux lines needs to be passing though the secondary coil. Air does not pass the flux lines (easily),the steel core passes the flux lines readily.
You can build the core two ways to take advantage of this: you can put the primary and secondary coils on two sides of an 'E' core, use the shunt to short out the lines of flux to the secondary. The more usual case is the primary and secondary are seperated by the air gap. Insert the moveable core, increased flux line count means increased amperage.
amdx wrote:

"amdx" wrote: So would the core be moving into an inductor on the primary of the ^^^^^^^^^^^^^^^^^^^^ It seems like it would make more sense to run the core in and out of the primary, because it has more turns of finer wire, but I never thought of that question, and I really don't know the answer. I would have a hard time getting mine out where I can look inside, so I will wait for someone else to answer, or for you to break down and open yours. I'll be interested in hearing what you find.

Think of the core as "stealing" some of the magnetic field. The farther in it's stuck, the lower the output current.
GWE

The transfomer is wound with the primary around one part of the core and the secondary around another part. With the moveable core ( MC )out the flux generated by the primary goes mostly through the core and links with the secondary. When the MC is inserted between the primary and secondary, a lot of the flux is shunted through the MC and never links with the secondary. That is the leakage inductance is greatly increased. The best way to think of it is adding an inductor to the secondary. With the MC inserted the open circuit voltage is the same, but the voltage droops a lot under load.
Dan

A tapped coil would be indicative of a constant voltage transformer, stick welders use constant current transformers. You can google easier than I can write for the rest of the info.

Most of the cheap buzz box stick welders are tapped coils. The venerable Lincoln "tombstone" AC225 is a prime example.
Jimmie D wrote:

Why don't you guys quit wondering and look at an exploded parts diagram in a manual? Most Miller welders' manuals are online, and lots of Lincoln ones too.
GWE

"Oxford" oil-cooled arc welders (commonly met here in UK) have a selector - well - a main range adjust and a fine-adjust - both of which have definite "switch positions". Seen one out of its oil bath. How does this work? Ones where you wind something in-and-out control how strong the magnetic coupling between primary and secondary is, don't they? So what is going on with this arrangement?
Rich. S.

The above statement is incorrect. I have seen many stick welders (CC) with tapped holes.
GWE