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11-19-2007, 09:52 PM #1
I understand that a CC welder is constant current and a CV welder is constant voltage. After looking at the wiring schematics for both welders I can not tell what makes one welder different from the other. Both welders are using a transformer, bridge rectifier, and reactor. The schematics look the same for the transformers. Does the wire feed make a mig CV?
11-20-2007, 12:00 AM #2
From what I understand CV has a way to sense arc gap and adjust the amperage accordingly in order to maintain that arc gap. Is there anything on that schematic that would look like some voltage sensor?
11-20-2007, 12:26 AM #3
A CC power supply is also know and a variable voltage power supply. There is no voltage regulation. Only current regulation. This is done a couple of different ways. The simples way is using a moving shunt through the transformer. Depending on the position of the shunt the maximum current out is regulated. Current an also be regulated with an external inductor.
A CV power supply varies the output voltage while allowing the current to find its own level. There is no current regulation only voltage. Simplest form of this is a tapped transformer and a switch or plug to jumper between winding in the primary or secondary of the transformer. Some designs use sliding brushes on the secondary to select voltage.
Many newer power supplies can do either CC or CV. Using either SCRs or IBGTs and sensing output voltage and current one can change between the two modes with the flip of a switch. For example the Miller XMT-304. They sell it in a couple different versions CC, CV, and CC/CV. Only difference is the front CPU board and how it processes and controls feedback to the switching IGBTs. Everything else is the same.
11-26-2007, 08:57 PM #4
Thanks for the info.
My old lincoln 250 AC welder has a transformer with several leads coming out of the transformer that are hooked to the dial that changes the amperage level. How is the current regulated? Is it possible to make this welder into a DC constant voltage welder so that I can run a spool gun off it?