My I ask a stupid question?

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I should know this..but....Why do most of the AC/DC welder have higher outputs in AC? I see a good number of smaller welders with ranges of 200AC/130 DC, 250AC/150 DC and so on.
Reply:when you rectify  AC, you only get 1/2 of each wave....David Real world weldin.  When I grow up I want to be a tig weldor.
Reply:So the 220 AC going is coming out DC and one half of the cycle wave is dropped out. Gotcha.  Thanks.
Reply:Sorry, wrong.  The rectifying in this case is the full wave, by using a 4-diode bank called a wetstone bridge.The current is limited in the DC operation because the diodes are usually smaller than can handle the full amount that the welder could deliver.
Reply:Originally Posted by MAC702Sorry, wrong.  The rectifying in this case is the full wave, by using a 4-diode bank called a wetstone bridge.
Reply:I looked at the manual for a Lincoln AC/DC225/125  http://www.mylincolnelectric.com/Cat...t.aspx?p=33322 Item #1 on the parts page and couldn't tell how they are wired.  No schematic.  I worked on a lot of battery chargers up to 300 amps.  They use + diodes screwed into an aluminum heat sink and - diodes screwed into another piece of aluminum.  3 of each(3 phase). If they only use 2 diodes, its not a full wave rectumfier.  Jportale, it wasn't such a stupid question.  DavidLast edited by David R; 10-04-2007 at 11:25 PM.Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Originally Posted by 69 chevyActually, that would be a modified Wheatstone bridge, no? ...
Reply:Originally Posted by David RI looked at the manual for a Lincoln AC/DC225/125  http://www.mylincolnelectric.com/Cat...t.aspx?p=33322 Item #1 on the parts page and couldn't tell how they are wired.  No schematic.  I worked on a lot of battery chargers up to 300 amps.  They use + diodes screwed into an aluminum heat sink and - diodes screwed into another piece of aluminum.  3 of each(3 phase). If they only use 2 diodes, its not a full wave rectumfier.  Jportale, it wasn't such a stupid question.  David
Reply:Over the years, I have built a couple of double wave rectifiers to convert A/C welders to D/C.  They produce a lot of heat so some of the loss is probably the result of resistance within the diode bridge, itself.
Reply:A full bridge rectifier, which is used in most welders, will convert both halves of the AC cycle into DC. There is a small loss of power but not very significant.  The current limit comes from the fact that the mfrs cheap out on the diodes and use components that are not rated for the full power that the transformer can deliver.   I am guessing also, that the mfrs take advantage of the fact that DC is most critical for low currents.  My Miller Stickmate is rated  220/120 AC/DC  while my IdealArc is rated 300/300.  The IdealArc if it were made today would probably cost 10x the price of the Stickmate.  The Stickmate is for sale, BTW355# Hay Budden3# Hofi HammerPropane ForgeIdealarc TIG 300/300AllStates Oxy Propane torchSmith Little Torch
Reply:Originally Posted by MAC702I thought there was something funny with my spelling on that; I kept getting flashes of someone sharpening an axe on it...
Reply:Dang!  You gotta axe to grind with me?  Actually, thanks for the correction.  I'd hate to do that twice...  Or, in this case, three times...