generator from an alternator?

[moody07747]

I was thinking of building a generator from an alternator to run my new welder...(a Millermatic 175)

this welder pulls 220v and 20 amps

is there any way to build a generator to run my welder and have an outlet for a 110V 20A outlet?

 

[chemelec]

Get an OLD Type Car Alternator, One that has a Seperate Regulator.

Eliminate the Rectifiers and Don't use the Regulator.
At about 4000 RPM on the Motor will give you 220 volts.

 

[Oznog]

At about 4000 RPM on the Motor will give you 220 volts.

But not at 60Hz.

 

[gerty]

Probably not 20 amps either.. I have a Miller 175 that I run off of a 5500w
generator, anything less and I think you'll be dissapointed..

 

[jrz126]

What motor would you use to turn it? You'll need 5.89812332 HP for 20 amps at 220V, assuming everything is nearly 100% efficient. (which it never is)


Does anyone know what the efficiency of a modern car alternator is?

 

[DigiTan]

It sounds like you're looking for a high powered DC-AC inverter. I've seen these used in small generator projects and most were designed to output the constant 60Hz you'd expect from a real-life mains. I don't know any models by spec. or name, but you can probably check with some generator or solar equipment retailers.

 

[Pyroandrew]

Does anyone know what the efficiency of a modern car alternator is?

30% is a good ball park figure for electro-mechanical devices. If you get any higher than that it is considered very efficient.

 

[chiba]

Inside a car engine bay the heat can do horrible things to an alternators efficiency. In an open air enviroment you can expect better results, I guess It would depend on your planned duty cycle and rpm of both the motor and alternator. In my setup for charging 12V batteries and solar backup for a beach shack i will be using a 120A Alternator driven from a 5.5hp Chinese Honda clone motor for 43%.

What are you planning to weld at 175 Amps?

 

[ante]

Why have the AC step in between? Why not just run the alternator directly like this guy?: **broken link removed**
Just a thought!
:roll: