Another HF 90 Amp Flux Core DCEN Conversion

[bob58o]

The first hurdle for me was removing the plastic screw that holds the grounding cable in place. The screw basically turned to putty the first time I tried to unscrew it. But I got it out!

I needed some more slack. This wire will get cut and the side coming from the transformer will go to 1 of the inputs on the rectifier. The other side of this cut (connects to grounding clamp) will go to the (+) Positive side of the capacitor (when I get it). A "jumper" wire will go from the (+) Positive output of the rectifier to the (+) terminal of the capacitor. So the grounding cable will be 5-6" shorter when I'm done with it.

 

[bob58o]

So I call Lowes to make sure they have 8 gauge THHN stranded wire. They tell me by the 500' ft roll. I says to the man, "But the website says by the foot for $0.59?" He says he has to check because they are getting out of the "by the foot" wire game.

He says they have some left in red, black, white, and green.

I go there to get some. I press the button for assistance, but nobody came. I cut myself off two feet and walked to the register. I explain that nobody came despite my pushing of the "HELP" button. I tells her 2 Ft at $0.59/ foot, 8 gauge THHN stranded Cu wire. She calls for a item number and a measurement. A guy walks up and asked if I was the guy who called earlier. I said, "I am." The guys says to me, "Just take it. We are getting out of the wire by the foot game."

So shout out to the dude at Lowes for giving me free stuff!!!!

Wondering how much I could get???? Enough to make a choke for the welder???? Don't really know how to make one. 25-30 turns of 8 gauge wire around a 2" Diameter 5" Tall Iron Rod???

 

[ezcome-ezgo]

We are witnessing the death of customer service.

 

[bob58o]

Removed the 3rd AC input terminal. Used an electric die grinder/dremel to grind it away. Drilled holes in case side cover. Mounted the rectifier using 10-24 x 1.25" screws with #10 washers, lock washers, lock nuts.

Peeled back a lil insulation and started cutting and crimping. Used crimping tool for 10 gauge cause I don't have one for 8.

 

[itsid]

One thing,
it's highly unlikely that any of the terminals short with the case the way you drilled and sized the holes (the mounting holes more than the terminal ones...)
BUT the most unlikely case will kick you in the behind if it gets the chance to do so
(say you carry the welder around, put it down and the rectifier catches on a toolbox, ripping out one mounting hole shorting a terminal with the case aaaand you're in trouble)

So, since filling everythign with silicone is a huge mess, how about some shrink wrap on the terminals for added insulation, it's cheap easy to add and just in case can protect you from some tingling sensations

'sid

 

[bob58o]

At 1:51 you can see this guy uses Heat Shrink on the Rectifier Terminals.
https://www.youtube.com/watch?v=8gL2_BuXcxg

I will probably heat shrink everything i can. I've got a assorted heat shrink kit from HF. LOL. I love the assorted kits. I walked to my buddy's house. I use his garage. I left the heat shrink in my car.

I made the holes for the terminals extra big. I even thought about using rubber grommets (I've got another assorted HF kit) but didn't want Rectifier sticking out any further. The grommets may be a good idea however, to provide space for air flow between the case and rectifier. The mounting holes and bolts allow a little play when not tightened down, but not enough to allow any terminal to short to the case. I dremeled one of the holes for a terminal a bit extra on top because my holes weren't exactly located correctly. I assumed the fours terminals were square. They aren't. One terminal was a bit close (not touching, but closer than the rest).

Maybe some heat shrink on the mounting bolts/nuts too.

---------- Post added at 10:13 PM ---------- Previous post was at 09:39 PM ----------

I do want to do some thing about this "third" terminal too. I should be worried about that one too, right?
Cutting Metal, Grinding, Welding, near the welder... worried a piece of metal will find its way to short this terminal to the case. I've got a bunch of RTV Silicone Gasket Maker stuff. I know I have RTV Red High Temp Temperature range -65ºF to 650ºF (-54°C to 343°C) . Don't think I've got any regular clear silicone adhesive.

 

[pRoFiT]

So once complete this will be a 90amp DC welder?

Will you set it up to switch the output + -. i know the 170 Amp DC model says to swap + and- when welding flux core or GMAW.

 

[bob58o]

So once complete this will be a 90amp DC welder?

Will you set it up to switch the output + -. i know the 170 Amp DC model says to swap + and- when welding flux core or GMAW.

That is correct. The welder comes AC. It is basically just a transformer. Flux Core is suppose to be DC and Electrode Negative (Ground Pos, Welding Electode Neg).

The DC Pos (+) output of the rectifier will go to the Pos (+) terminal on the 50V 100,000 uF capacitor then to the grounding clamp.

The DC Neg (-) output of the rectifier will go to the Neg (-) terminal on the Cap and then to the welding electrode.

It doesn't matter which AC cable coming from the transformer goes to which input on the Rectifier. Pick any two you want, then switch em. It shouldn't matter.

The wire feed system works off of the AC, so make sure when you cut the wires the wire feed wires are on the AC side of the Rectifier.

Looking into a "bleed" resistor to drain the capacitor after I shut the machine off. Not really sure how to size this resistor.

 

[pRoFiT]

Well its looks good so far. I would think 40-50ohm resistor with a large wattage rating. but maybe some more research on what others are doing.

Are you adding gas to the mix?

These are the two things i want to do to my 170Amp. Gas and a capacitor to help smooth out the power. no need for rectifier on mine.

"Borrowed" my moms old helium tank that is empty and the local gas shop said they can swap for argon. so i need about $60-$90 for gas and another $80!! for valve. but i think i can get valve online for under $30.

I really want TIG machine but they are out of my price range for my hobby.

p.s. thanks for the engine build thread. helps me sleep at night. im on page 6 i think.

 

[bob58o]

No Gas. I like that it is simple. I don't need to worry about gas tanks and I can move it and plug it in anywhere.

I use Lincoln wire and upgraded the grounding clamp to the HF 400 watt clamp. I took off the MIG nozzle (no gas, no need for the nozzle) and use Lincoln tips.

I'm still researching inductor coil / chokes. Maybe going to try to build one at some point.

https://www.harborfreight.com/400-amp-welding-ground-clamp-66708.html

 

[bob58o]

I've seen people say to use a DC computer fan instead of a resistor.

I like this one, but not sure how this will do with my 50V capacitor set up.???

This 120mm x 25mm 24V new case fan has two ball bearings for long life, a 3 pin (2 wire) connector, and 4 self tapping mounting screws.

The specifications include;

Voltage, 24V
Voltage Range, 12 to 26V
Current, 0.22Amps
Speed, 3300RPM at rated voltage and zero pressure
Flow (Max), 75CFM
Noise, 30dBA at rated voltage and zero pressure, measured at 1 meter to side

http://www.ebay.com/itm/120mm-25mm-...586814?hash=item58d0588f3e:g:FUkAAOSwbqpT6l1w

or this
http://www.ebay.com/itm/Fan-24V-DC-...or-/272281830785?_trksid=p2141725.m3641.l6368

Use some 3" 6-32 screws and put the fan 3/4" in front of the rectifier heat sink. Fan is ~1" thick. Rectifier/heat sink is about 3/4" thick (not including terminals) Figure I could use some nuts as spacers.

Not sure if the specs would work.??? 24V 0.22A?? With the capacitor...

Aluminum Electrolytic Capacitors
Manufacturer United Chemi-Con
Series U32D
Capacitance 100000µF
Tolerance ±20%
Voltage - Rated 50V
ESR (Equivalent Series Resistance) 6.8 mOhm @ 120Hz
Lifetime @ Temp. 2000 Hrs @ 105°C
Operating Temperature -40°C ~ 105°C
Polarization Polar
Applications General Purpose
Ripple Current - Low Frequency 31.43A @ 120Hz
Ripple Current - High Frequency 35.2016A @ 50kHz
Lead Spacing 1.126" (28.60mm)
Size / Dimension 2.500" Dia (63.50mm)
Height - Seated (Max) 4.125" (104.78mm)

 

[bob58o]

So a little more research and it seems like the max AC output of the welder is 28 Volts. DC output of the rectifier should be around the same right?

Not sure if all 24V fans are ok at 28V or just the ones that say 28V. Some fans listed as 24V say 12-28V.

I think this fan would work. Dual purpose. Cool the Rectifier during use. Bleed the capacitor after. Need to post it here before I forget what I like.

EBM PAPST 4214NHHR 24VDC AXIAL FAN 120mm x 120mm x 38mm
http://www.ebay.com/itm/EBM-Papst-4...mm-/112230642990?_trksid=p2141725.m3641.l6368

12-28 Volts
313 mA
7.5 Watts
Ball Bearings
120.7 CFM
3500 RPM
49dBA
12" Connection Leads

$14 shipped from California

Its a little thick for the 3" Screws I wanted to use to mount it in front of the heat sink. I'll have to find 4" screws and maybe make a bracket to support the fan

Would love to find a fan that said 28V and was 120mm x 25mm with a guard for the less than $20 shipped. But if any 24V fan will work, then I could use this one I posted earlier
http://www.ebay.com/itm/272281830785?rmvSB=true
Fan 24V DC 120 x 120mm 25mm 0.25A 2000 RPM fan with Guard and Connector

 

[bob58o]

28V Computer Fan Capacitor Discharge GAB

So if I put a 24 V, 0.313 A, 7.5 Watt Fan between the capacitor terminals....

P=I^2*R
7.5 watts = R* 0.313Amps *0.313Amps
7.5 = R*0.098
R= 76.5 Ohms

Then to figure out the discharge time from 28Volts to say 1 volt...

R= t / ( ln(V(t) / V(0))*C)
t = time in seconds
V(t) = Voltage at time equal to "t" seconds
V(0) = Voltage at time equal to "0" seconds
C= Capacitance in Farads
ln() = natural log of (_)

R= 76.5
V(0)= 28Volts
V(t) = 1 Volts
C= 100,000 uF = 0.1F

Choosing V(t) = 1 Volt allows us to find the amount of time in seconds it will take for the voltage to drop from 28V to 1V.

76.5 = t / (ln(28/1)*0.1)
76.5 = t / (3.33*0.1)
76.5 = t / 0.333
t= 76.5*0.333
t= 25.5 seconds

So the fan will discharge the capacitor to 1 volt in 25.5 seconds. I can live with that.
A 12W (0.5A) 24V fan might do it in 16s. That would be similar to a 48 ohm resistor (which is in the range of Profit's guess/suggestion) unless I've got this whole thing wrong.


Now the question is How Does Running a Fan pulling 0.3A - 0.5A from the capacitor while welding affect the weld quality? I'm guessing it is insignificant.

 

[ezcome-ezgo]

Now the question is How Does Running a Fan pulling 0.3A - 0.5A from the capacitor while welding affect the weld quality? I'm guessing it is insignificant.

The effect on the weld quality is proportional to the impact of GAB on a fan in a 10:1 ratio.

 

[itsid]

if by coincidence you have two 12V Computer case fans laying around;
just wire them in series and give it a test...
if you're happy with that and don't want no push pull config of fans (can be very efficient though) you still have time to order a 24V fan

'sid

 

[bob58o]

if by coincidence you have two 12V Computer case fans laying around;
just wire them in series and give it a test...
if you're happy with that and don't want no push pull config of fans (can be very efficient though) you still have time to order a 24V fan

'sid

I think I may have some of those laying around. I may or may not have used 12v case fans for cooling / exhaust on an alleged stealth indoor "tomato" grow box.

16 CFL's in a 24" x 24" x 48" cardboard wardrobe box gets pretty warm. The fans didn't help too much. Wanted 70 degrees F, got more like 90 F.

Homemade activated carbon filters made using nylons, stack-able wire pencil holder cups, and fish tank activated carbon. Tomatoes get stinky. LOL

 

[bob58o]

Terminalater-2 Judgement Day

Terminals Crimped.
Added the shrink wrap.

A little worried about the wire from the gun reaching the negative terminal of the capacitor. I think if I take apart the wire feed mechanism and strip some of the outer jacket on the welding lead, I can get extra length. It isn't as simple as the grounding clamp side.

It should be fine, I hope. It'll be tight. Cap is 4-4.5" tall. Wire needs to be bent so the ring terminal fits. Just hope I don't break the ring terminal trying to connect the wire to the cap.

I could always just mount the cap at an angle or how ever I need to.
Was just planning on vertical mounting with the bottom of the cap on the bottom of the case.

 

[itsid]

I've seen people extending or rather "moving" the ring terminals to a more convenient location,
by adding a piece of copper pipe
(flattened in a vice, internal gaps filled with solder and shrink wrapped afterwards)
drilled to accept the cap's screw terminal on one end, bent to reach to a convenient location, then drilled and tapped to provide a new screw terminal where it's easier accessible.

basically making bus bars from pipe

talking of which, maybe you can find some copper bar stock in your local hardware store,
to skip all that flattening and filling.

And yes, massive copper since a multi strand wire needs to be three to four times as big to be as efficient.

'sid

 

[bob58o]

This is the capacitor I just ordered...
https://www.digikey.com/product-detail/en/united-chemi-con/E32D500HPN104MDA5M/565-3298-ND/2095912

It cost $42 shipped.

The SQL150-1200 3 Phase Bridge Rectifier w/heat sink is less than $14
http://www.ebay.com/itm/3-Phase-Dio...d=262633099410&_trksid=p2047675.c100005.m1851

(10) 8 gauge Ring Terminals $7
http://www.ebay.com/itm/8-Gauge-Gol...099599?hash=item33c48ff04f:g:4eEAAOSwnHZYSxMX

24VDC Fan
~as low as $7, maybe $15
http://www.ebay.com/itm/DC-24V-2Pin...953549?hash=item3a952e774d:g:FCgAAOSwQItT4zNX

HF Heat Shrink (I had it already)... $5
https://www.harborfreight.com/127-piece-heat-shrink-tubing-set-67524.html

2' 8 gauge stranded copper wire (Freebie, but would cost $2)
https://www.lowes.com/pd/Southwire-SIMpull-8-AWG-Stranded-Black-Copper-THHN-Wire-By-the-Foot/3129533

Screws Nuts Washers Bots,.....$5

All together probably just under $200, I think the welder was $110 with tax (maybe cheaper).

So like I already knew, this will end up costing more than the 240V 170 amp HF mig welder, but should do better than the stock AC welder and I can still use it with 120V outlets. Plus it gives me something to do. Just using a rectifier can be done much cheaper.

I just ordered the Cap. It was on a two week back order.

 

[ezcome-ezgo]

Hello