home made 3 phase power converter

[ns_in_tex]

I have done something similar to this in the past, just guessing at what I was doing. Several people on tbn got my juices flowing & did a google search & found written instructions on building 3 phase power converter to use when you only have single phase current available.
Check here:
http://www.metalwebnews.com/howto/ph-conv/ph-conv.html
for more info.

 

[bgott]

Will these home made phase converters run a welder? I was at a bankruptcy auction a while back and there was a few screamin' deals on three phase welders. Sure would have liked to bought a couple.

 

[ns_in_tex]

I honestly don't know that much about the converters, so I would be afraid to say.

 

[chipmaker]

From what I have been told from folks that have them, they run a 3 phase welder just fine. (Referring to rotary type not static convertors) There is a formula to figure out what size is needed. Powering equipment is much easier as you put hp against hp for what you need, and don't really need to pay attention to amps, as much as you would have to in powering a welder. Amps and volts and watts etc all fit into the picture and there are fomulas out there to figure it out. I see what I can find out.

 

[pasquali]

I work in a small machine shop which is powered soley by phase converter. We had a local guy build this using a 20hp motor and we can run all our machines at the same time, (surface grinder, old heild id/od grinder,air compressor,mill,lathe) the way I understand it is that the single phase incoming power connects to a series of capaciters which gives it the needed start up power and then takes minmal power to keep it spinning. the biggest load on this system is start up on our lathe. Fortunatly we have a lathe that the motor stays running and it uses a clutch for foward and reverse of the chuck.

 

[bgott]

I know how to figure out watts and compare them. I just didn't know if there was some funny load factor with welders I didn't know about. Something like with motors running on, for example, 10 amps but needing 15 amps to start.

 

[Dabota]

I have an uncle who is retired now, but he had a very simple 3 phase converter in his small machine shop. Had an old 3 phase motor sitting on the floor that was plugged into a single phase outlet in his shop. His motor would not self start so he would give the shaft a kick with his foot to get it spinning. Once the motor was running his 3 phase lathe would start just fine.
I'm not recommending this, I expect it fed unwanted waveforms into the distribution system from his local utility, but it sure was a simple way for him to get his lathe operating.

 

[Soundguy]

The capacitors and associated windings are what is causing the phase conversion. Think of it like geometry in the electrical world. Both capacitors and inductors can shift phase.

Back in the 80's, A friend worked at a grocery store. We had a tornado come through town, and all the business's lost 3phase power. We rigged their main freezer to run on single phase in much the same way that has been discussed here.

Soundguy

 

[wallysue]

The idler motor on my converter is mounted on a post outside so you don't heve to listen to it run and it takes no room inside. It's a 10hp enclosed fan cooled motor with the shaft cut off so no one can get tangled in it. It runs a 5hp compressor, 3hp lathe and a 7 1/2 hp pressure washer all three phase and not at the same time. At first it used a voltage relay for the start circuit but now I have a timer relay instead. It has been no problem since, a couple of seconds gets it going. Never tried a welder with it but I've read it takes a really big converter to do it. There have been some posts about the welder stuff over on the www.chaski.com machinist board.

 

[bgott]

http://www.gwm4-3phase.com/index.html

This site has a ton of information on phase converters. It also has info on power company transformer sizing and has a few schematics. The're not homemade but I combined this stuff with the homemade sites and came out with a clearer understanding of how they worked. The prices on the store bought converters ain't cheap!