Turning AC welder into DC with a rectifier

Finally got around to this one. Bought a 200amp single phase rectifier and attached it to the AC welder. Have to admit it welds much the same, arc might be a little nicer. If anyone know what size capacitor to use for smoothing I'd appreciate the info.

[@nvidiashield3757]

I just bought a New Lincon 225 AC. Paid $400cnd. Spoke to a welder of 30 years and said just leave it AC. DC is not good if welding equipment that is magnetized also suffers from Arc blow problems. Always a place for AC. Been around for decade's. Bullet proof machine.

[@DavidMcLuckie]

Smashing. I spoke to a welder of 40 years and he says that AC has it's place, but if you understand the reasons then DC 9 times out of 10 produces the better weld. So whatever works best for you is the best choice.

[@jackcantrell791]

Thank you guys for all your input I enjoyed that

[@cicerocorreia1309]

Ficou muito bom parabéns pelo seu trabalho

[@6lr6ak6]

I converted a clarke 230 te turbo welder to DC, my mate got me a load of 7018 LH rods, and l fitted dinse connectors so l can also TIG weld using pure argon. It's scratch start, with gas valve on the neck of the torch. Get really good welds. Just to add to this message, the clarke was ok after conversion, but after using a Parweld inverter l sold it and bought the Parweld XTS 163, it's absolutely great.

[@marcinciech2450]

Would u say it welds better than before conversion?cheers

[@paulandrulis4672]

Add a large 8uf 200A 36V capacitor, around $35 on ebay. With the amperages used, the smoothing capacitor has to be of as high of microfarads (uf) as possible since the greater the capacity, the smoother the output DC under full load. Also, some rods require electrode negative and others electrode positive, so keep that in mind. 2 pairs of cheap female internal welder plug sets makes your unit either or (AC or DC), as well as easy electrode positive or negative. Smoothing capacitor, full wave 200-300 amp rectifier, 2 sets (4 units total) female welding connectors + cheap AC welder = high dollar AC/DC unit capabilities. The smoothing capacitor connected across the DC (Capacitor lug '+' to Lead connector '+') leads stabilizes the arc, providing stored current to the leads when the current from the welding unit drops into the "humped" waveform (actually a form of pulsed DC). You will probably have to run a little hotter on the welder output dial, since the current stored in the capacitor is drawn from the current supplied by the welding unit with each pulse. A person can use a 200 amp alternator, a 6.5hp gas engine, and a 3-phase 300A rectifier to make a really, really, nice portable 200A dc welding unit using this technique, without the need of smoothing capacitors, since with the three phase output consists of 3 different output waves that overlap each other by 120 degrees, giving almost straight line DC output with just the rectifier.

[@DavidMcLuckie]

Thanks for that. I was actually curious about building a petrol welder. Very helpful information there.

[@paulandrulis4672]

@@DavidMcLuckie Glad you found it useful. With the gas engine though, remember an alternator requires exciting voltage to work (unlike a generator which has permanent magnets), so you will need a small 12v SLA (sealed lead acid) battery to power the Stator terminal to get electricity. You can pick up a 7AH on fleabay for around $15. You don't need a full sized car battery since you won't be running a starter, A/C fans, or headlights off of it. A jumper wire can be run from the rectified output + back to the battery to keep it charged. Also remember that alternators use the case as ground (-). The "B" terminal on the unit is +. The L terminal is for a gauge or idiot light on the dash, so you don't need it.

[@charlesgallegos3575]

Paul Andrulis are the any plans for this type of Build?

[@345rvv]

Hello. what kind of capacitor is that ??. The capacitor parameters are capacitance and voltage, no ???? I am planning make the same, I already have the rectifier and plan make a choke coil with the core of a microwave. But investing the open circuit voltage of welder is about 120-130 V, so the capacitor must be 200V and for the high currentes of a welder (60 - 150 Amp) need a capacitance in many thousands of uF, near Farads itself, so a 8uF capacitance not will smooth or filter much..... Or maybe I am missunderstanding something, do you already do something ???

[@paulandrulis4672]

@@345rvv Yes, microfarads and voltage are the two main specs used concerning a capacitor for selection. The higher the microfarads for a given voltage the better for a smoothing capacitor when converting AC to DC. When specs like amperage are listed on a rating, it is a specialty cap, capable of safely discharging up to the amperage rating listed. Not all capacitors are equal considering such things as terminal lug amperage ratings, etc.

[@contact4mwy7]

I converted my welder from AC to DC and found that with electrode negative (like yours) that there is less splatter and more heat/penetration put into the work piece. Think of it like a magnet in that through AC it attracts and repels at 60 times a second (50 hertz where you are?) and through DC it is always in an attracting mode of the weld metal to the work piece. As for your capacitor, carefully measure your AC voltage at the terminals with the unit turned on. On my 90 amp unit, the AC voltage had a highest reading of 27 volts. The capacitor I used was rated 21,000 microfarads and up to 100 volts DC, well above the 27 volts output.

[@345rvv]

Hello, I am planning do the same with a Lincoln AC-180 welder. I measure in CD after the bridge rectifier, in open circuit, and have 110-130 VCD, (in 110 Amp the selector) I know that must drop that voltage to 25-30V when soldering, but for that above 100V open circuit voltage, need use 150 or 200V capacitors.... or not ?? this cause that I realize (sadly) the capacitors to use are huge in voltage and capacitance .... or I am missing something ??? What voltage capacitors you used ??

[@yeliab814]

@@345rvv best to get 150v or 200v caps. 200v 1000uF caps have gotten cheaper because a lot are manufactured these days as a pair of them are commonly found in USA market HVAC/furnace blower motors . If you only can get 100v rated then perhaps place a 100watt, 100 Ω aluminum shunt resistor permanently across the welder DC output (after bridge rectifier). Turn on welder and see if this pulls voltage down to 100 or less. Quickly strike arc and don't leave welder on except when actually welding. Experiment with resistor value as required . The resistor should protect the caps i'm open circuit but won't draw much power once the arc is struck and voltage plummets lower .

[@joserincon7338]

Saludos, muy buen video. Una pregunta: ese rectificador se recalienta?? O mejor dicho sirve para trabajar bastante tiempo?? Soporta trabajo pesado??

[@zaidhussain5206]

Thank you for sharing this video

[@mrelectron6220]

As some one else suggested you need a choke on the output it will help smooth the dc wave form you could than think about adding some capacitance to the supply before the choke. Otherwise the capacitors are useless by themselves you would need such a large amount capacitance for the amount of current draw you'd effectively would need a car battery to smooth out the wave form if the output voltage was 12Vdc. Good video to get people thinking about ways to convert their buzz box over to DC.

[@Bodragon]

Not at all. I'm doing a conversion to DC and I've calculated that I can get the AC ripple down to 0.9 volts using a collection of 40 x 10F, 2.7V capacitors connected in two parallel banks of 20 caps in series. These caps are going for £1.80 per 5 so will only cost £14.40 in total. I know 40 caps seems like a lot but they are quite small and will easily fit inside my Juba MIG130 welder. I have based my calculations on a maximum voltage output of the welder at 54V DC with a current of 90A.

[@stefanopassiglia]

@@Bodragon Where'd you get those caps that cheap? A 10F cap is pretty expensive (2-3 euro). What's the total capacitance then? 20x10F in series is a huge one!

[@Bodragon]

@@stefanopassiglia eBay. If I could upload a screenshot I would. Save to say that the seller was one: trail-blazer21_ru I bought these caps way back in October 2018 so I don't know if he's still selling same at present time. Good luck!!!

[@345rvv]

@@Bodragon Hello. Do you mean 10 Farads capacitors ??? So, 20 caps in series result in a equivalent of 0.5 Farad, two series in parallel results a 1 Farad ??? ok?? not bad. The voltaje that supports are 54 V ok ??. I have a Lincoln AC-180, and planning do the same, I have the 300 Amp bridge, and planning use a choke coil with the core of a microwave oven transformer. Calculating the capacitance I realize that need a huge capacitance for thar currents. Measure my welder in open circuit after the rectifier and have 110-130Vcd, (with load , soldering, must drop to 27 - 30V) but for that open circuit voltaje above of 100V, need capacitor of 150V or 200V so I realize (sadly) that need a super bigger capacitor... Or I am missing something ???

[@Bodragon]

@@345rvv If you have two capacitors in series, each takes half the voltage. So if you have 20 2.7V caps in series, the total string of capacitors can handle up to 54V (That's 27 x 2.7V) >

[@thomaswilliams4417]

Great info an demo thanks

[@gbs7144]

Any idea what output voltage and amps are while DC? Or the range?

[@tompayne8863]

I like your shop! It looks like mine... a mess! If you don't do anything, you won't make a mess... hahaha!! My 200 amp AC buzz box has welded a lot of stuff. I don't see a reason to go to the trouble. If it ain't broke, don't fix it! I enjoyed your video, though.

[@DavidMcLuckie]

I agree 100% with you. If you've already got a welder that works, why change it. I just wouldn't buy another one. Ah yes, the mess. I like to tidy occasionally. Usually, once I've 'finished' a project.

[@kremnin]

Try using a Electrolytic Capacitor 22000uf/100V Screw Foot, or even up to 47000uf/100v. You can even go as low as 60v Capacitor. But I like to overkill on everything. I also use a 400 amp bridge rectifier . I did my spare 100 amp stick welder, and my spare MIG welder. on the MIG, I can swap the pos & neg around for stainless steel. Just try stuff on old welders, the worst thing that can happen is you make a brown s#it stain and let some smoke out. Good luck guys.

[@Rypaiz]

Would the 22000uf 100v capacitor be wired on the + of the DC output from the rectifier?

[@malcytull]

An interesting & informative video, I have been thinking about doing this to my old SIP arc welder, do you think it was a worth while project? many thanks for posting.

[@DavidMcLuckie]

As a few actual professional welders have commented, these old welders will practically live forever. Giving them a DC output improves them. The only thing missing from my setup is a large capacitor to smooth the DC even further.

[@malcytull]

@@DavidMcLuckie Thanks for your reply David, you're good man !!

[@terrencewalsh453]

@@DavidMcLuckie Why not a choke coil instead?

[@charlesbetts9777]

For your capacitor try a 50 volt 22,000 Mfd. You can pick them up with screw terminals.

[@francoscanfe9627]

5o volts sono pochi

[@jimviau327]

What capacitor? Assuming the welder put out 30Vrms Dc and 3Vac ripple is the desired result : 8mS , 3V = 400V/s : at 100A/400 = 0.25 Farad. That would be a BIG expensive capacitor. One would be better off to use a powerful choke. One cheap solution could be to use the armature of a MOT with 4 turns of a 3AWG wire. Much cheaper, more robust and more durable. ( calculations are approx. )

[@345rvv]

Hello, I am planning do the same with a Lincoln AC-180 welder. Have the 300amp bridge and planning use a choke coil with core of MOT (hope put more than 3 turns). I measure in CD after the bridge rectifier, in open circuit, and have 110-130 VCD, I know that must drop that voltage to 25-30V when soldering, but for that above 100V open circuit voltage, need use 150 or 200V capacitors.... or not ?? this cause that I realize (sadly) the capacitors to use are huge in voltage and capacitance .... or I am missing something ???

[@jimviau327]

Raul Valenzuela , yes you are missing something. The idea of using an inductor instead of big Capacitor is to avoid having to utilize a big , high voltage Capacitor all together. The usual configuration when DC is required is to utilize a Cap in parallel with the output of a rectifier bridge, so as to reduce the ripple effect of the rectifiers. A similar result can be achieved using an Inductor. The configuration then would be different. You need to connect the inductor in Series with the rectifier bride output such that the inductor regulate the output current (hence reduce the ripple voltage) . No big Capacitor is necessary then.

[@royspeakman1157]

BRILLIANT !

[@allornothing7957]

Here’s a question for you, I want to rectify my 2.7kva petrol generator to charge a DC lifepo4 battery bank. Where would I look to find what specs etc I need? And what’s the best way to control the voltage?

[@DavidMcLuckie]

I'd never dissuade anyone from trying to build something of their own but charging batteries, that's technical. You've got voltage, current, sensing, cell ballance. Although I would be interested in seeing your results.

[@allornothing7957]

@@DavidMcLuckie yea I know, its only because I have the spare generator etc. Watch this space!

[@robertneighbors4091]

What matters is how the different versions weld with 7018 rods . . . .

[@my2centz196]

I'd like to know is it easier to strike and maintain with DC then it is with ac I have a cheap ac welder which works fine but sometimes I do have trouble getting started. Once started runs fine but could be smoother. This could be all inexperience but wondering if DC would help improve this.

[@DavidMcLuckie]

In theory yes, but I still have trouble sometimes starting either. Some of the DC machines have a feature that's supposed to make it easier to start. It starts with a high current for an instant to start the arc then drops back to what you set. DC should be smoother as the voltage isn't crossing 0v at any point. As a shitty welder myself, the switch to a DC machine certainly helped me make not just quite so shitty welds. :)

[@zanpekosak2383]

@@DavidMcLuckie Higher frequency is the most important part. The voltage is second and current last as far as striking goes if Im correct...

[@anakjampangl9016]

​@@DavidMcLuckie solution kapasitor 400uf 250vac

[@rodbicke]

The basic idea is fine BUT THOSE BIG BRIDGE RECTIFIERS CAN DISSIPATE 500W. BOLTING IT TO A STEEL CASE WONT CUT IT, it needs decent heatsinking otherwise after a few minuts it will revert to ac as the diodes melt down. I am just doing one and mounting the bridge on a 1/2" alluminum plate 150x250mm and a spreader 3mm plate the size of the welder side. That is only enough for a couple of minutes burn, at a time, for no more than 10% of the time.

[@DavidMcLuckie]

The test was to see if you could.

[@erwinsummer6164]

you need to add a choke after the DC output,i used an old microwave transformer core. wound it with 6 turns of #4 welding cable. works great. you can use cap's but there not really neceasary ,as this is not a DC power supply.

[@DavidMcLuckie]

Do you use one with both wires wrapped or one per wire?

[@erwinsummer6164]

just one side. doesn't matter which side. made the arc easier to start.

[@svetko05]

ERWIN SUMMER Can you tell me how much amps is your welder. I'm currently sourcing parts for mine which is 160a and i was looking online what wire gauge to use and some site claimed I'd need 00 gauge wire, which is ridiculous.

[@erwinsummer6164]

mine is a lincoln 225 i used #4 gauge.

[@Lasurge1982]

Would this be the same as other videos I’ve seen where they add a huge capacitor after the bridge rectifier to bleed off the bridge?

[@ayebee1207]

Hello Sir! From the States. For the LC filter in your D/C output welder. May I suggest a D/C Link[motor drive]Poly film capacitor: 800v 220uf @75A forward and 400A max surge. A Sendust, flat wire, fixed Inductor, rated forward @75A continous. Using the above, I calculated 1mv of D/C ripple and forward voltage of 17.2vdc on my Chinese 125A wire feed welder. @27v no load. My machine: 60hz. 115vac on a 20A breaker. Your on 230V 50hz. Correct? Perhaps using four stud diodes fixed to a 6.35mm aluminum plate for a heatsink, rather than the encapsulated rectifier? I have read others conversion comments where the bridge has failed when placed inside the welder cabinet. A surplus metal boxto house the additions perhaps. I Enjoyed your actual demonstrations of the before and after. Cheers!

[@ayebee1207]

The online calculator I used, has the choice of 50 or 60hz. So you can input your input frequency For your D/C ripple output voltage with the cap rating you use.

[@DavidMcLuckie]

Thank you, thank you, thank you. Actual numbers and products that people can use to build their own. Have you got a link to the calculator and I can post it here?

[@ayebee1207]

Here is the link: www.zen22142.zen.co.uk/Design/dcpsu.htm I recommend not using Ebay components due to manufacturer reject, or knockoff fakes. Your quite welcome.

[@aaronbenns9051]

Some rods are optimized for ac or dc

[@irishguy200007]

Did that come from the first terminator?

[@oscarvalenzuela262]

Good job David, excuse me, why dont use a capacitors after dc convertion, they help the Ripple minus, excuse my english!! Thanks

[@DavidMcLuckie]

Your English is perfect. The only reason I didn't use one is because I didn't have one. But you should use one as you say to reduce the ripple.

[@Lasurge1982]

I’ve seen other people add a capacitor also after the rectifier for bleeding off the system.

[@anotherdave5107]

? prior to adding a cap there is no energy stored so there is nothing to bleed off. Adding the cap gives storage so a resistor across it is used to bleed of the stored energy.

[@XPFTP]

caps are not for bleeding off... resistor across the caps do that.. caps are to smooth out the DC valleys. so they almost go away ... more KuFs the more the valleys will be filled in and smoother voltage... smoother voltage gives a smoother weld.. so inbetween the DC peaks.. there is a valley.. that is what the caps remove..

[@ronaldopinili2246]

Where did you buy that rectifier?

[@DavidMcLuckie]

Good old eBay.

[@ifell3]

Your a good welder!!!!

[@DavidMcLuckie]

Thank you. But I'm just an OKish welder.

[@ronalddino6370]

@@DavidMcLuckie small Miller welder plant gives me problems it have to make noise or build up to weld If not no welding can produce

[@miketyne2771]

Supplier brand of AC -DC rectifier used in the clip ?

[@calvinhandley2373]

China, you can find them on eBay.

[@davidevans9462]

Is the Bridge Rectifier 200 amps single phase? ...Are you running on an ordinary 13 amp single phase?

[@DavidMcLuckie]

Single phase yes. AC in DC out. Just normal plugged into domestic mains 13 amp.

[@franciscovaldez8354]

No lleva "capacitor"?🤔

[@rickharding7209]

Can you please say rectifier a few more times for me? It some kind of asmr with that accent

[@brunobastos5533]

stupid question why not rectify the input lead 110v or 220v that run at lower amperage . Output less volts but run higher amperage. And this is the second vid where the got the stick on negative why? iam a welder and learned that ground is negative and caliper is positive and switch for tig

[@DavidMcLuckie]

You have to turn AC to DC after the transformer. Transformers don't work with DC. As for lead polarity if you're a welder then you'll know you can swap them for a variety of different welding applications.

[@brunobastos5533]

@@DavidMcLuckie thanks , i know but 7018 do not like reverse polarity , and make shallow and low penetration welds

[@francoscanfe9627]

non te ne intendi di elettricita' ? per fare un simile discorso

[@mara69323]

why neg. paralleled to pos. out and also pos. to neg. out....

[@hardcoreplayafromthehimala4888]

Can full bridge rectifier be putted before welder - after grid?

[@DavidMcLuckie]

Negative. The transformers inside the welder only work on an AC input.

[@PaulAlford75]

Reekris - are you leaving those terminals as bare metal for electrocution purposes?

[@DavidMcLuckie]

+Paul Alford As bare as the earth clamp and electrode. :)

[@Void-tw6sx]

maybe 40v 100a with wet hands will do if you touch both terminal at the same time but no harm if you just touch only 1 terminal.

[@juangaytan8798]

Buenas tardes como puedo conseguir ese rectificador y como pedirlo que precio tiene

[@345rvv]

Hola, yo lo compré en ebay, de 300 Amp para que este sobrado (los hay de 200 Amp y 150 Amp mas baratos). A mi me costó 26 dolares y pasadito de 30 con el envío a Mexico, desde china. A como esta el dolar y la conversión siempre a su favor de paypal, pagué como 700 pesos.

[@brucehildreth8155]

Get an old Microwave transformer and wind a choke out of number 4 wire,, smooth that DC out

[@michaelthorpe9560]

what you should have tried fitting in this circuit is a bloody big none polarized smoothing capacitor just before the rectifier,, then you would have had a nice smooth flow of DC current to the welding rod!,, but the volt's to the welding rod would have been a bit higher than normal as the capacitor would have held them up when discharging,,,, PS,, do you know a way of welding ""wood?"",, I only ask because I am crap at wood work,, and if it could be welded I could do more job's better when using wood!

[@emerybooker6335]

5000F capacitor should work roughly

[@acklan3]

Did you mean 5000 MFD?

[@emerybooker6335]

acklan3 yeah

[@alihadi1978]

Does he need Condonsateur

[@scottmcbride2237]

The more capacitors you add, the nicer the weld will Look and lay

[@joserincon7338]

Pero donde se agregan los condensadores??

[@christophertedeschimattar32]

You supposed to install a capacitor too. Do it and will be much better!

[@niladrisekharjana1957]

Why do not use capacitor

[@DavidMcLuckie]

Because I did not have one.

[@9q7a5z]

Do you know why these welders hum? Because they dont know the words!

[@irishguy200007]

Do I need a welding mask to watch this?

[@DavidMcLuckie]

No. Your screen isn't capable of generating dangerous UV or IR, or brightness.

[@lancerudy9934]

16 pounds is how much in us money?

[@danbywater6333]

Change the polarity so positive lead is in neg position and you will see a big difference a player everything will be smoother

[@DavidMcLuckie]

Please correct me if I'm wrong on this. DC Electrode Positive for better penetration and thicker material, DC Electrode Negative for thin material and sheet work?

[@contact4mwy7]

I heard it as the opposite of that from other videos by actual welders. You are right to use mostly electrode negative for most jobs, and only switch if you have thin metal or a project that heat would affect.

[@DavidMcLuckie]

From TheFabricator.com: In DCEP the electricity flows into the tip of the welding rod and concentrates about two-thirds of the heat, which gives good penetration. DCEP is usually used on thicker steels.In DCEN the electricity flows out of the rod, concentrating about one-third of the heat on the rod. Less penetration makes this a very good choice for thinner steels.Not sure what direction the rectifier I bought actually puts out, but one-way rounds gives me even shittier welds than the other way. :)

[@contact4mwy7]

David, after reviewing more videos I have found that you are correct. I have found conflicting examples when using Flux Core MIG, which is what I have, probably to keep the slag out of the weld. Carry on!

[@DavidMcLuckie]

Ahh, MIG, Gasless MIG (whatever it's real name is) and TIG differ again on polarity. It's like welding is like science and stuff. :)

[@officialmysteriousrider6327]

Dc is way better to weld than ac

[@yovangeorgiev9607]

I don't see any point of converting AC, especially for welding thin tubes. A lot people mastered 6013 on AC and if you start DC you will have hard time to control the arc blow. If you use magnetic holders the situation is very bad. Better to have smoke and spatter than arc blow.

[@chenzitong1]

Depends on the situation, i use both ac and dc with stick, depending on the rod. I mainly use 7016 rods, although not much any more as tig is so easy to setup these days... i do see your point though, for a non professional or occasional welder its a new learning curve

[@eliford2258]

needs a copasitor

[@TheChewy78]

The current flows from the positive to the negative just like a truck battery. . DCEN is when Current flows from work piece/ground clamp into the electrode holder when it is DCEN/straight polarity. DCEP is when current flows from the POSITIVELY CHARGED electrode holder into the NEGATIVELY CHARGED work piece .

[@DavidMcLuckie]

www.thefabricator.com/article/arcwelding/smaw-basics-how-much-do-you-knowr This is the source of my information.

[@snowflakemelter1172]

Invest a few quid in some clean steel FFS !

[@DavidMcLuckie]

Buy clean scrap metal. Check.