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Arc Welder: AC Transformer with a Sliding Shunt Core (Fanger, US 2,248,070)
An AC arc welder is a step-down transformer whose current can be turned up and down. H. J. Fanger (US 2,248,070, 1941) cuts a gap through one leg of a laminated ring core and slides a laminated iron shunt bar through it: pushed in, it carries flux past the secondary and lowers the welding current; pulled out, the current rises.
For arc welding he gives about 60 to 68 volts open circuit, 15 to 200 amps, dropping to 38 or 40 volts at the working arc, with a small coil on the shunt bar in series with the secondary.
Source: H. J. Fanger, "Welding Transformer", US Patent 2,248,070 (filed 1938, granted 1941). Picture: its Figs. 1-5.
Advanced
Unknown
Instructions
1
1
Read Fanger
Read Fanger
"With arc welding, infinite control of the volume of the secondary current, between maximum and minimum is obtained by adjustment of the slidable shunt core without altering the welding characteristics of the current, also better ignition of the arc is had at a given voltage, and greater stability of the arc".
2
2
Stack the core
Stack the core
Build a single rectangular ring core of insulated iron laminations, held together with brass (or insulated) bolts or rivets in insulating tubes (Fig. 4). Cut a gap straight through one leg, accurately machined and finished, and make a circular joint through the opposite leg with the segments staggered to overlap in successive laminations. Core size, lamination iron and thickness are not given (ours: the tools).
Materials for this step:
Unknown Metal1 iron laminations
Hex Bolt Assortment1 brass bolts
Unknown Insulating Material1 insulating tubesTools needed:
Tin Snips
Drill Press
Drill Bit Set
Files (Hand File)
Unknown Dimensions3
3
Make the shunt bar
Make the shunt bar
Make the sliding shunt section of the same laminated iron, a snug fit in the gap with its laminations edge-to-edge with the core's, and long enough to fill the gap at every position. Sheath both sides with a slightly wider plate of Bakelite that overlaps the edges of the gap to guide it. Fit a threaded rod on its outer end, working in a nut fixed to the section (or move it by hand, with calibration marks along one edge).
Materials for this step:
Unknown Metal1 shunt laminations
Bakelite2 side platesHex Bolt Assortment1 brass bolts
Threaded Rod1 piece
Hex Nut1 pieceTools needed:
Drill PressDrill Bit SetFiles (Hand File)4
4
Wind the coils
Wind the coils
Wind the primary and secondary windings on both legs of the core (Fig. 2), in series or in parallel to suit the line voltage and the current wanted. Wind a small auxiliary coil round the shunt bar's path, fixed so the bar slides through it, and connect it in series with the secondary through a reversing switch (some jobs weld better with the current through it one way). Turns and wire sizes are not given.
Materials for this step:
Copper Wire1 insulation and size not givenTools needed:
Unknown Dimensions5
5
Spring the joints
Spring the joints
On both sides of the gap and of the circular joint fit pairs of confronting angle plates, held by brass bolts in insulating sleeves and drawn together by spring bolts whose heads rest on slightly arched spring plates, so the joints close snugly on the sliding bar. A small lever on the gap-joint nut gives a half turn to release the bar for moving. The angle-plate material is not given.
Materials for this step:
Unknown Material4 angle platesHex Bolt Assortment1 brass and spring boltsUnknown Insulating Material1 sleeves
Spring Steel Strip1 arched spring platesHex Nut4 piecesTools needed:
Drill PressDrill Bit Set
Adjustable Wrench6
6
Connect and set
Connect and set
Connect the primary to the line through a line switch, and the secondary leads to the electrode holder and the work. Pull the shunt bar out for more current, push it in for less: Fanger gives about 60-68 volts open circuit and 15-200 amps, dropping to 38-40 volts at the arc.
Materials for this step:
On/Off Switch1 line switchTools needed:
Adjustable WrenchMaterials
10- 1 shunt laminationsPlaceholder
- 1 brass and spring boltsPlaceholder
- 1 sleevesPlaceholder
- 2 side platesPlaceholder
- 1 piecePlaceholder
- 5 piecesPlaceholder
- 1 insulation and size not givenPlaceholder
- 4 angle platesPlaceholder
- 1 arched spring platesPlaceholder
- 1 line switchPlaceholder
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