Alternator welder

[blasphemy000]

I kinda skimmed through this so I'm sorry, but what diode trio are you talking about removing? The ones for the regulator or the ones for the output? I've never delt with a regulated alternator, I'm a Mopar guy so all my alts are external even in their automotive sense. The internal output rectifier will handle whatever the alternator can throw at it though. Most diodes that are rated at high amperage are also rated for a voltage way higher than what anybody would need for welding. I have some diodes here I was going parallel together to use to convert an old "buzz-box" to DC and they are 60a and I think 600v each. I never had my alternator apart but I'm sure the voltage on the rectifier diodes is way higher than the alternator is capable of putting out even when there isn't an arc struck. If the thing has regulator diodes separate from the output diodes then I have no idea about those as I've never had to work with an internally regulated one before.

[Rivets]

I kinda skimmed through this so I'm sorry, but what diode trio are you talking about removing? The ones for the regulator or the ones for the output? ......

Blasphemy,

Yes, they feed the "+" side of the coil on a GM "N" type regulator.
Packaged as a trio, each one connected to a stator phase junction at one end, and the other ends connected together to feed the coil.

See schematic in post #38 above.

Cheers,
rivets

[parkour]

You can check out the schematic of the GM alternator.. http://mightymo.org/public_html/imag...re/DelcoSI.jpg It appears to me that the diode trio provides an isolated, lower voltage drop path for self excitation current to flow so that the alternator can self start without an external power supply being connected, while at the same time loads are attached to the main alternator output. (it's plausible for a 70's era vehicle that such a thing would be important) The residual polarization in the rotor should be enough to get it going. This is how cheap self "regulating" mains power generators work (residual mag, not diode trio)

It would be a trivial matter to convert this to a self starting (no external electric supply needed), adjustable constant *voltage* supply. You could make it a current limited supply (like a buzz box) (more like constant power than CC or CV)) by powering the field externally from a stable power source, or if you add a current shunt (precision low resistance resistor (usu just a spec length and gage of copper)), and some control circuitry, you can make a voltage limited, current regulated supply.

I did this with a 12v power system, LM393 comparator, mcp14e4 mosfet gate driver, and an FQP50N06L mosfet. The circuit switches the field on and off to give me an auto selecting voltage or current regulated supply. I read two potentiometers with the 393, and also the output voltage and output current. When both were below the set point, the circuit would switch the field on, but when one or the other got above set point, the circuit would switch the field off. The current shunt I used was 4' of #4ga copper, and dropped 1mV per amp of current. I selected that to minimize power dissipation at the 400 amps of output I was designing for. It's still 160 watts lost in 4' of copper at 400 amps.

[bobwills]

Well last night i hooked it up and put a pair of jumper cables on it to see if it would weld. It didnt. But it was just on my little test motor. So might build a little mount to try it on a bigger motor that will turn it much faster so i can get the full output out of it. That or take the diod trio out of it so i can control it. Lol. But dont know where to start on that or what it looks like. What yall think i should do.

[bobwills]

Yeah the diod trio did what i needed it to and thats to make it to where it is controlable by a riostat not by engine speed. And might just need to kick up the amps on charger. And i made it to where the regulater is grounded to the outside so i can just unhook it if i test it with it not grounded so i dont have to take the thing apart again.

[Rivets]

Yeah the diod trio did what i needed it to and thats to make it to where it is controlable by a riostat not by engine speed. And might just need to kick up the amps on charger. And i made it to where the regulater is grounded to the outside so i can just unhook it if i test it with it not grounded so i dont have to take the thing apart again.

Hi Gabe,

The alternator output is determined by BOTH the alternator RPM, AND the Field Current as applied through your rheostat.

Also, remember that at the end of the day, it's not the regulator itself that needs to be grounded, but one end of your rotor coil. The grounding lug on the regulator is just a convenient test point.

One end of your rotor shaft has two copper slip rings and two associated brushes. Electrically, the simplest way is to ground one of the brush wires and connect your rheostat control to the other brush wire. That's it. The regulator has no longer any function electrically and can be completely ignored. It can even be removed if it allows you to perform the brush connections that I just mentioned.

HTH,
rivets

[blasphemy000]

I read your post about you only getting negligible voltage with 2 amps applied to the field. There is something wrong with your setup. If I apply 2 amps to my field I have enough power at the torch to weld .030-.045" steel. I know your alternator has a lower amperage rating than mine does but you should still be more than 1v at the output. I still think you are better off finding a 90A(They make aftermarket ones with more power) Chrysler alternator from a '90s car with the 3.0L Mitsubishi engine. The Chrysler alternators have no regulator and the two terminals on the back of the alternator go directly to the brushes and into the field coils. I think it would be much easier for you to get it wired up and working that way rather than having to worry about the internal mods you are having to do with this one.

[bobwills]

Yeah i did wire it feild and sensor wire together. Maybe if i seperate the 2 though it might stop. Need to try that next chance i can. If its that way ill put another switch on the sensor wire so when i want it off i can just flip it off too. Im not really sure though

[bobwills]

Well i went ahead and removed it. And it did just what I needed. When i turned the field off the output went off. But it wasnt putting near the output out it needed to be puting out. Only a little over 1 volt and before it was 50 something. But i only had 2 amps running to it. Next chance i get to work with it i will try 10 amps or something. But i also grounded out the voltage regulator. Not sure if it needed to be cause with it i already was getting over 50 volts.

[I_Love_Plasma]

You might want to try one change at a time. That way you know what does what, to what. Do you get "what" I mean? Seriously that's a lot of "whats". Since your diode trio is gone you should be pumping out 3 phase AC depending on what you have done it may only be single phase. So try flipping you meter to AC volts and take reading, you should be making quite a bit of voltage. Even 120V right out of the wall has up to 5VDC piggy backing on the AC sine wave. If you are getting 28+ volts AC try getting a 3/32" rod to burn at full blast what ever you can do. If you want to make it DC you'll need to get a big rectifier ~ 100 AMP - 600V rated probably cost some where between 30-60 bucks.

[Rivets]

....Since your diode trio is gone you should be pumping out 3 phase AC depending on what you have done it may only be single phase...

ILP,

No.

His diode rectifier bridge (6 heavy duty diodes in the case) is still intact.
His output is DC if that bridge is OK.

The diode trio was only to supply DC to the rotor coil via the regulator.
He is now supplying DC to the rotor coil via a controlled external source.

Cheers,
rivets

[I_Love_Plasma]

ILP,

No.

His diode rectifier bridge (6 heavy duty diodes in the case) is still intact.
His output is DC if that bridge is OK.

The diode trio was only to supply DC to the rotor coil via the regulator.
He is now supplying DC to the rotor coil via a controlled external source.

Cheers,
rivets

Oh I see now thanks for the clarification.

Cheers,
ILP

[bobwills]

Ok i see what you mean I think. Do you run the field exciter wire to the brushes or the output to it. And if i do that do I need to unhook it from the regulator or is there no need to.

[parkour]

To the brushes. You can leave it hooked to the regulator.