Welder generator

[rosietheriviter]

I have an Onan welder/generator model CW251-C, 220V 10KW generator, 350 amp 78VDC welder that was manufactured in 1956. Runs like a top, 2 cylinder, air-cooled, gasoline powered, 30+PSI oil pressure, 90PSI compression.

My questions now are about the generator and alternator.
The alternator is close coupled to the engine and when the gen/weld selector switch is in "power" mode the engine runs at 1800 RPM. Voltage and frequency are a product of RPM and are not regulated otherwise on this unit. 4 pole with 2 slip rings.

The generator is on the same shaft (one piece shaft) and when in "weld" mode, increases the throttle (governor) setting to 2300 RPM giving a rated output of 350 DC Amps with an open circuit max of 78 volts.

It has a fairly small bridge rectifier, a fairly large transformer and 3 coils that are maybe one inch in diameter - 6-8 inches long with one connection on each end. The weld/power switch closes two contacts that go to or from the welding control reostat.

My biggest question is - since the unit welds AND will generate 110+ and/or 220+ volts AC (simultanously), without the battery installed, one of the rotating devices must be magnetically excited? Should I be able to tell if one of the components attract steel (magnetic)?

Does any one know or willing to venture a guess as to whether welding at 1800 RPM (rather than 2300 RPM) will result in a substantially lower than otherwise expected voltage, amperage, or both? Or is it more likely that the 2300 RPM is required only for the increased power output from the engine?

I think I can send pictures of the unit and of the individual components if that would help answer the question.

Thanks in advance,

Rosie