Three Phase Converter Question

[Farwell]

You answered any question that I might of had about a 3 phase welder. If I see one for sale cheap, don't buy it.
Thanks
Farwell

 

[v8dave]

A cheap, quick and dirty 3 phase converter can be made from a 3 phase motor.

Cheap: Get another 220V 3 phase motor.

Quick: Hook the 220v single phase mains across two of the three motor terminals. Hook the three phase "output" across all three motor terminals, yes this means two of the three terminals will have two wires on them.

Dirty: The motor will not self start! You need to somehow start the motor turning in the direction stamped on the motor. Here is how to start the motor turning Building a Three Phase Converter. I knew of a guy who just mounted the motor low and just kicked a pulley on the shaft to get the converter motor running. I'd recommend against that, especially since a push button capacitor start is so easy do as described in the link.

CAUTION, bolt the motor down. If you don't when it does start to spin up, it will roll and wrap up the wires creating an electrical hazard. It will also roll when the end use motor is loaded down.

You don't use the motor to run anything, it just makes the three phase power. It's the basis of a "rotary 3 phase converter."

This approach is only good for up to several HP motors. You aren't going to be able to run a 10 HP 3 phase motor off this scheme on normal house wiring. The link points out, use a HP of converter motor for each HP of end use motor.

Your mileage may vary, use this approach with caution. If you are not comfortable with electricity do attempt this. As a cross check to make sure converter motor size is big enough, check the converter (motor) temperature to make sure you don't burn the place down.

 

[AntrimMan]

v8dave Oooohhhh Deeeee, that page is exactly what I was looking for. Thank you very much. Now, in between drunken stupors, I can sit down and rationalize the machine tool requirements.

Farwell Do not despair, not all Bridgeports are 3 phase so you can still have hope. Mine is 220v single phase, it's an oldie but does everything I need. There may be optional motor voltages / phase available as spare parts. Just keep your eyes open for one that suits you. Maybe you can have 3 phase run to your garage. I failed after having a wee-wee contest with the building inspector. He wouldn't allow a separate service entrance to the garage and also forbid 3 phase into the residence. Patience paid off and a 220v model materialized.
Another thing to watch out for is voltage requirements. Most of the 3 phase tools I look at need 477v so a boost transformer is also needed, and so the final the cost continues to rise.
If you get real serious and do your home work you will find what you want / need, out there some where.

All the best,
Martin

 

[Jim57]

I purchased a three phase air compressor to add to my paint shop. I am not sure if it can be converted or not. I will go out and take some pictures of it and post them. Maybe someone here can tell me if I wasted my money. I surely would like to get it operational.


Jim

 

[Farwell]

I have considered having a 3 phase drop added to different places I have lived but always come back to the expense. I have reached the conclusion that it would be much cheaper to purchase a new single phase motor or if I was really serious, go the phase converter route. I priced a 3 phase drop in my California residence and the cost was approximately $2000 just for the hook-up and there was a minimum monthly cost. I can buy several single phase motors or several converters for that price.
Farwell

 

[Farwell]

Dave,
Thanks for the link and information.
I have always wanted to build a phase converter, if for no other reason than I have a few 3 phase motors that are just gathering dust and I am a build it my self nut. I may never use the phase converter but it will sit on a shelf along with all of the other projects and everytime I see it I will remember having built one.
Farwell

 

[Farwell]

Jim,
The cost and size of larger horse power single phase motors have dropped considerably over the past several years. If the compressor itself is in good condition and will pump the amount and pressure of air you need, I would go the new motor route. Do not know if a phase converter will take heavy start load required on an air compressor. Maybe someone else can answer the load start issue.
Farwell

 

[ns_in_tex]

Jim, Years ago I took an old 3 phase, 4 ton air conditioner compressor & used it as an air compressor on single phase. It was junk, so I didn't have anything to lose.

I got several run capacitors (2 or maybe 4) & hooked them up in parallel to one leg of my single phase supply, then connected the other side of them to the 3rd leg of the compressor. I did not have a unloader valve on this setup, so it had to start under pressure. Sometimes it would fail to start, so I took a couple of start capacitors, hooked them up parallel along with the first start relay I took out of the junk box, and it never looked back.

It ran that way for several years. My main problem was keeping oil in the compressor, since this type tends to pump the oil out.

If you are considering buying a new motor and could get access to somebodys junk pile on capacitors & relays, I would certainly try this first.

 

[Taylortractornut]

My old highschool shop teacher had a setup like that several years ago then when iI went through his class he had started a shop. We got to build his converter. somehow he later wired his machines all over to extend the usage of some others that went past his original HP ratings. Youd see 2 mills in a line with gaurds over the quills running and he's be at on in on a blanchard grinder or cutoff saw while some one else was running the big lathe. I think the 2 idling mills were being used as a slave motor. I also working in a shop that had one and they used an old tiller frame witth the motor still on it to start the slave motor.

 

[MadReferee]

Here is a link to the Practical Machinist discussion forums. They have a forum specifically for phase converters and VFD's. Take a look. There are over 8000 posts and you will find many interesting discussions.

Practical Machinist Discussion Forums