120vDC to 120v AC invertor

[Chris]

Hi all,
I have tried searching for a solution to no avail. I have an older Lincoln
welder that is generating 120vdc to a standard outlet. At the start I
thought it was AC as power saw would run fine. Not until I tried to hook up
a cap start compressor did the smoke tell me something was wrong. After
checking everything I could check, I in fact learned that it was a true
generator as it was creating 120vdc. How the saws are running I have no
idea. Unless they are universal motors??????

Now I come to my question, getting the DC to AC. Actually the term inverter
might be wrong as I do not need to change voltage. Should I be asking for
an oscillator? Either way I need to get the DC into a sine wave. Not too
picky how true it is, I just need it to run motors, more or less, at a home
construction sight (read no solid state running off of it).

So is there a simple circuit I can devise, or any off the shelf solutions I
can use? Keep in mind that the unit is rated at 15amps = 1800 watts (BTW no
breaker or fuse on it at all, which I will correct). 1800 watt new
generators are about $400 or less, so keeping it under that cost would be
nice.


Any pointers, help, flames, appreciated.

Thanks,
Chris

 

[Chris]

Sue,
Yes I was thinking about a UPS. I have an older one lying around. Almost
tempted to just plug it in and see how it likes seeing only DC coming in.
Umfortunly it has two 24dc batteries, giving 48vdc to the controller. Step
down transformer comes to mind. I have a few, but the closest I have is
120v down to 80v.

What to do,
Chris

 

[Chris]

Sue,

You caught me on the transformer. I am still thinking that it is AC coming
out of the welder. Still cannot beleive that they would bump that much DC
at 15 amps out to a regular AC plug (yes it was designed that way, way back
then). Worse yet, no breaker or fuse.

Chris

 

[repatch]

Frankly, with what you've said in this post I think the best course of
action would either be to drop the idea completely, or at least hire a
professional to do the work.

Transformers don't work at DC, they tend to blow up and start fires...

 

[ehsjr]

Hi all,
I have tried searching for a solution to no avail. I have an older Lincoln
welder that is generating 120vdc to a standard outlet. At the start I
thought it was AC as power saw would run fine. Not until I tried to hook up
a cap start compressor did the smoke tell me something was wrong. After
checking everything I could check, I in fact learned that it was a true
generator as it was creating 120vdc. How the saws are running I have no
idea. Unless they are universal motors??????

Now I come to my question, getting the DC to AC. Actually the term inverter
might be wrong as I do not need to change voltage. Should I be asking for
an oscillator? Either way I need to get the DC into a sine wave. Not too
picky how true it is, I just need it to run motors, more or less, at a home
construction sight (read no solid state running off of it).

So is there a simple circuit I can devise, or any off the shelf solutions I
can use? Keep in mind that the unit is rated at 15amps = 1800 watts (BTW no
breaker or fuse on it at all, which I will correct). 1800 watt new
generators are about $400 or less, so keeping it under that cost would be
nice.


Any pointers, help, flames, appreciated.

Thanks,
Chris

I would say be prepared to give up the idea. A PC UPS will not work
for you, unless you intend to use low power motors. Your compressor
probably needs FAR more power than a typical PC ups can provide.

You might be better served by buying a generator sized to your needs.

Ed

 

[Chris]

I would say be prepared to give up the idea. A PC UPS will not work
for you, unless you intend to use low power motors. Your compressor
probably needs FAR more power than a typical PC ups can provide.

You might be better served by buying a generator sized to your needs.

Ed

Already canned the idea for the sake of safety.and cost plus I still have
the welder.
Actually the UPS that I have is good to 2250watts, more than enough to drive
a 3/4 hp compressor.

Thanks again all,
C

 

[Don Kelly]

Already canned the idea for the sake of safety.and cost plus I still have
the welder.
Actually the UPS that I have is good to 2250watts, more than enough to
drive
a 3/4 hp compressor.

Thanks again all,
C

--------------------

Can it handle the starting inrush current?

 

[ehsjr]

hook up


solutions I


(BTW no




Already canned the idea for the sake of safety.and cost plus I still have
the welder.
Actually the UPS that I have is good to 2250watts, more than enough to drive
a 3/4 hp compressor.

Thanks again all,
C

Doubtful. Do you know what the compressor will draw
when starting?

Ed