Dual alt for increased amp?

[DieselWarrior]

I am not familiar with the setup, so I am researching. Ive had real good success with accurate information from users here.

The two alts will be hooked to the same driver, and will have the same RPM, both alts will get the same voltage for the field exciter.

My desire is to "double" the amperage of the total output.

This will be used in a welding environment with a small engine or motor to drive them.

My desire is about 150 (or more?) amps of PURE DC, which is hard to do with transformers or inverters.

This will end up being the power source for -Stick -MIG and -TIG welding.

Feedback, comments and advice are all welcome!

Thanks,
Andrew

 

[sixb]

Can't really help with any tech. stuff but I have 2 100 amp alternators from a acucv with brackets for sale, pm if interested.

 

[sweetk30]

i have a 200 amp single alt direct bolt in and works great. 120 amp at idle also.

http://www.alternatorparts.com/

just one of many places.

 

[zombie1969]

Are you smoking crackAn altinator will burn out quick if run a full output for too long.

 

[Fordum]

I have seen things like this tried. In theory it will work, in practice, not so much. Usually you wind up burning out one of the alts.
Even though they both get the same exciter current, one or the other is usually a little more sensitive to it.
One extra wrap in the winding would probably be enough. Or one solder joint better than the other.
Which causes one to take all the load.

But, most importantly, don't forget why they are called alternators. Its because they put out alternating current.

HANG ON, everybody read the rest first.

The old generators actually put out DC by having brushes and a commutator.
The drew the output from the rotor through the brushes, which limited how much power they could put out and still fit under a hood.
Alternators turned everything inside out by tapping the voltage off the field coils and controlling the magnetic field of the rotor to control the output of the fields.
However this produces AC, which is why the old stuff did not use it.

When cheap effective solid state diodes showed up, alternators became practical.
But, there was a problem with ripple.
The diodes converted the AC to DC, but there was a point when the voltage switched from positive to negative that there was no voltage being put out.
So, modern alternators use 3 phase AC so to use the third phase to "fill in" the gap. This gives you a cleaner output, but you still have little peaks and valleys in the voltage.
That is the "alternator whine" you sometimes hear in radios.
Crank your truck up turn on the radio and turn the volume all the way down.
In most cases you can hear a faint whine that will change in pitch as you change the engine speed.
If the two alternators were not phased correctly, and I have no idea how you would go about doing that without using a chain drive or gears, then one is going to be making a peak when the other is making a valley.
Which will cause problems.

If you need pure DC in the multi-hundred amp range, don't forget that a good truck battery can output 3-400 easily.
Most welders have duty cycles anyway, so using the alternator or a good heavy duty battery charger to charge the battery in-between cycles will probably give you what you want.

Plus, don't forget, you are trying to re-invent the wheel.
http://www.premierpowerwelder.com/

And, yes, I am trying to re-invent the wheel too.
http://www.readywelder.com/

 

[DieselWarrior]

Im coming to the conclusion, if I *do* decide to go the alternator route, a single unit will be better.

I am also looking at the DC Cheater, I may just get it and hook it to my existing buzz box and just forget everything else.

http://www.proto-power.com/dc_cheater.html

Then Ill be able to run MIG, TIG or ARC (AC or DC) with one power box.


I was hoping to run a 12hp gasoline with the alternator so I could have portability too, but.... looks like its going to be way more expensive than just buying a trailer off Craiglist and bringing it to the house to weld!

Andrew

 

[diesel4me]

I bought a old "Lincwelder" with am Onan 2 cyl engine off CL for 125 bucks that needed engine work,sight unseen...had it running the next day,it had a stuck exhaust valve..but it still needs work,that cylinder smokes and it raps some,but at least I know now that the welder/generator works well and its worth fixinbg or getting another engine for it..

I was tired of my AC buzzbox welder always tripping the breaker every time I cranked it up higher than 75 amps,our 220V curcuit was only a 20A one going to the garage,and it would cost me 500+ bucks to run a proper cable to the garage,not only that I tired of hearing about the electric bill going up every time I welded something..
I figured with this machine,I not only have DC welding capeability & 110V AC power,I can plop it in my truck and weld anywhere,and only use a gallon or two of gas..

I looked into making a "Weldanator" ,but by the time I gathered up a suitable altenator,engine,made a cart,etc,I would have more than the 125 bucks I spent on the Lincwelder invested--and it still might not work worth a dam,or go up in smoke in short order...the "ZENA" altenator welder is about the only proven one I've seen that holds up for any length of time..the home brewed ones might work for awhile,but I doubt they live for long running stock diodes ...

 

[Blue85]

You could keep one alternator for regular duty and build a "weldernator" out of the second one. Somebody posted detailed instructions here a while back, but it's a trick that goes back decades.

I wouldn't want to weld with a source that is in common with the rest of the electrical system. You might fry the engine controller, radio, etc.

I have had dual alternators in parallel for probably 5 years with no problems. Sure, they will never share the current demands equally unless the load is really high, but why does that matter? It's still less work than the single would get. It's also close to double current at all rpms. The drawback is that it takes up more space that could be used for an air compressor or welder.

Some "performance" alternators offer big current at high speeds, but are worse than stock at idle. IMHO idle is the limiting factor anyway. Others are better at all speeds, but they will never be cheaper than the second stock alternator.

As for your wiring diagram above, keep the signal lines separate from the output cables, but otherwise wire each line on one alternator with the same line on the other.