Would I need capacitors ?

[Colas LeGrippa]

Hi boys and girls,


I know this board is dedicated to tube amp building but this is a capacitor tweaking question that only.the best techs  here will be able to answer.



I own a  Lincoln ELectric AC-225 arc welding machine  ( called the buzz box , no tubes, only the transformer hey hey ).
I would like to convert it to DC, easily done with
a SS bridge rectifier, just like we do in a tube amplifier. The max A is 225 so I guess a 400 A bridge would do the job well.
Question : would I need some kind of capacitor
on the DC side ? The welder operates at aprox 75 V.
Thanx.


PS : naked girls, motorcycles, welding machines...we know everything at Hoffman amps

[shooter]

the only thing I  do welding is hurt myself 

[Colas LeGrippa]

My coat once caught in fire while cutting with an acetylen torch...

[acheld]

A question from Colas can not be resisted -- even if I have little capacity to answer the question!

Is clean DC w/o ripple a necessity for DC welding?   My bet is that large inductors are used; but capacitors would have to be quite large (physically) and expensive, it seems to me, are probably not used in consumer devices.

I bet there are schematics available out there.   Rob Robinette, I'm sure, has one available.  Maybe not.

[SILVERGUN]

Here's the most simple schematic I could find.This goes back to the 70's and the schematic hasn't changed much over the years.D1 and D2 diodes are STRAIGHT POLARITY(SP) and D3 and D4 are REVERSE POLARITY(RP). The ratings are 85 amp/ 300V each. These diodes MUST BE mounted to a heat sink and usually come as a one piece part or "output rectifier assy."
The caps you see are only there as protection caps, not filter caps. The value is .01uf / 500V.
R1 and VR1 combine to form a SUPPRESSOR and the entire DC + path goes through a large STABILIZER (Z1). R1 is a 3.9K 2 watt resistor and the Varistor is a .6 watt / 175 V

[DummyLoad]

https://www.mouser.com/datasheet/2/427/vs-ufb211fa40-1769585.pdf


2 of the above should work. forced air cooled VERY LARGE heatsinks required. 


--pete

[SILVERGUN]

https://www.mouser.com/datasheet/2/427/vs-ufb211fa40-1769585.pdf


2 of the above should work. forced air cooled VERY LARGE heatsinks required. 


--pete

We usually see this type used on the low voltage/high current output side of the inverter power supply after the AC has been switched to high frequency (block diagram pictured).

The 2nd snip is a view of how this type are used in circuit (D1,D2) and coupled to a boost circuit

[Colas LeGrippa]

Thanx amigos ! I should have checked Youtube b4 posting that thread. There are already bridge rectifiers circuit mounted in a box , for AC welding machines.  4 screws , 2 in 2 out, which they sell for 50 bucks or so.
So no hassle !
I ll order one soon. But before I got to finish my Christmas gifts:  I am making "TRACTION AIDS" for my daughter, son, best friend and for my neighbour,  Rocco"pitbull" Tremblay ,before he gets mad  at me (the magnum 357 or 45 special guy ). ( I can t make the difference between a slingshot and a  shotgun ).  Definitely I ll have to move  out of here. Last week when I asked the landlord to fix the bath taps, he told me to fix them myself cause he  knew nothing about taps...Samething with my kitchen counter top.


Don t worry, I do no rod welding in my apt..I would already be dead, not by breathing the fumes but by a gun bullet in my head. When I gave my house to my children thinkin I was goin to die  soon, I kept the garage for my tools and motorbikes cause I wanted to leave  them to my son. When the doctor told me my health was perfect,  I was very happy. All I needed then  to feel healthier was new spark plugs and oil change.   I had to rent an apt where to live.
3 miles away from my garage.

[jjasilli]

I'm sure we can help make your welding machine louder!

[Colas LeGrippa]

With a quad of KT88