Hi freq welders and Plasma cutters

They are lower cost and lower waste . Commonly the transistors are in a wasteful configuration and can easily be switched to a single NPN configuration .
Cheap diodes can be added in many places to shut down quickly , in case of hot spots in the circuitry .
They all can be adapted to wire feed , allowing dynamic control of current to the wire .
i dont like company i bought the 518 welder from . Simon K of Longevity-inc.com refuses to fix his web site .
Try phoning in ur order ..
518 has the full range of voltages to do all welding and plasma . But you need to beef up the input capacitances by 2000 microfarads . simply place these across the existing caps , but place new caps so they get 310vdc . and observing correct polarity . Now you can plug into 110vac , and get full power .
Simon K , uneducated in electronics , said 110vac option makes lower weld power . Its simply voltage sag at the input caps . These caps droop too much as the transistors feed the transformer . on 110vac , if there is even a trace of hi OHMs , such as a line cord less than #10 , the caps cant get the energy .
The old welders had transformers that were too expensive to control their voltage . Today , a MJE13007 is about $0.15 and controls 1000 watts ,
But since they ARE businessmen , they install IGBTs costing $25-40 .. IGBTs get 10 times hotter for the same power .
My 518 has foot control , so i tossed the hvy box in the trash , mounted the small "pots" in the torch , now i do Stck , TIG with a control on the output .
Im welding thin , and i pull the trigger to strike the AWS60111 at 100 amps , release it all the way , and i get 20 amps to the 1/8" 6011 .
SWEET !
BTW , the MOSFETs are vulerable in the half-bridge config , so , place them or MJE13007's in parallel at transformer primary ( input ) ,, rearrange drive circuitry ...
Motorola clearly shows the half-bridge to be the only dangerous config for Power MOSFETs . Its for the accidental diode in all mosfets , but missing in bipolars ...
Harbor Fright has a $200 E-welder that uses the industry std IGBT's . They simply waste more power, need a bigger fan . I have 5 . They use the 3525 current mode controllers , simply shut off the surface mount NPN's , the chip drives , to get a better control of power transformer . It has a huge Feritte transformer , it has a low Curie temp , so if it gets warm , it may fail . It must get direct air from a fan . Fortunetaly the huge copper wires in it are heat sinks , arrange thesee wires so fan pushes air over these bared wires ..... The output diodes are 8 in parallel , calculate a small OHM resistor to place in series with each , maybe just use smaller wires . Calc it such that at max power , they drop .05 volts . This is enough to equalize the load on the 8 DIODES so ya cant possible burn them . Another diode could read the temp at each output diode . Thermal shut down
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