Hey Phil...normally the secondary is shorted to make the transformer more effective for ballasting. When the secondary is shorted, the "load" is reflected back to the primary to create " more current control" when used as a ballast. If the secondary is open, the current control seems to be more so of core magnitizing current flow leaving you with very little current capacity or core saturation issues depending on core design.
Since the primary needs rewinding, keep the design as it is, utilizing the slide. Short out the secondary, and rewire the primary with wire thick enough to handle the current requirements of the load you intend to draw through the hi volt transformer.
If the core of the welder is able to be separated, you shouldnt have too tough of a time rewinding.... if it isnt, then rewinding is going to take some time
be patient, dont kink the wire....One last thought.... you can rewind the core as a standard inductor IF the center leg is of substantial size and the core is an EI configuration. Expect about 3 amps current of each square inch of center core leg measure... example, center core leg is 3X4 ( 12 sqr inch) this gives you approximately 36 amps of current control. Wire to consider would be solid copper core at about #8 with THHN insulator jacket.
Also, if you leave the secondary of the welder in place, you need to pay attention to the " duty cycle" listed on the welder. The duty cycle is a Time On/Time Off cycle depending on current flow through the secondary. If the duty cycle is exceeded, the windings of the welder will go into melt down and let the smoke out ;)
Scot D Phil Tuck (hvtesla) wrote:
Hello. When using a welder for ballast it is normal to short the secondary leads as this increases the inductance of the primary considerably, but why does it increase it? The reason I'm asking is that I have an old 160 amp welding transformer, the sort with the secondary one side and the primary on the other with a slide in between. What is the best way to rewind this as a ballast coil with this setup. (The existing primary needs rewinding anyway) 1) Wind a new primary coil to achieve a suitable inductance and leave the existing secondary in place and short circuit it.2) Wind a new primary and a new secondary and connect them in series.Bearing in mind I still wish to use the slide to vary the inductance I'm not too sure if the second method would be very effective. Phil _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________ Tesla mailing list Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla