Using a 3 phase compressor in a 1 phase shop?

[rnscustom]

Forgot about the pressure switch cost . I have 2 compressors one with a pressure switch on / off and the other with a motor starter and separate pressure both IR 5hp , one single stage 3450 and other two stage 1725 ( this is the bigger unit with the motor switch separate ) . Just replaced the pressure switch after 12 years so that's probably the cheapest way to go $79

 

[Lelandwelds]

That motor would cost twice of what the OP can get the compressor for.
I have my setup since I too got my 3Ø compressor very cheap.

Now that I'm done writing this, I look back, wow, what a waste Rant. Nobody's going to understand what I just said, except for A half-dozen electrically sound . 99% of electricians I run into just think I'm speaking Spanish. The worst part is is I'm not electrician by trade!

I am glad you wrote it. I (and others) will come back and read this some day when needed.

I think I would have done it. A severe duty 5 hp single phase WEG or Baldor or Leeson will be $500 and the whole rig will last nearly forever. (Class F insulation and 1.15 or better) Probably be the most reliable electric machine in his shop. Finger valves get poo poohed by the armchair quarterbacks but I thought were really easy to replace ( ridiculously overpriced by IR though)

I am interested in something similar. I want to take a 3 ph 10 hp and repower it with a 5 hp. I'm hoping to swap motor pulleys and turn the pump @ 550 or 600 rpm. (Slow as I can and still get a good splash.)

The VFD that I have seen are about $700 for one large enough to run this compressor.

 

[Caa311]

Should have went with the VFD!

 

[Lelandwelds]

Why VFD?

They cost more than a single phase motor. VFD cause electrical noise and are hard on some motors. You cant really vary the speed too low due splash lube issues. I think a smart variable speed to respond to variable demand would have to be a homebrew. I dont know how and dont know a source.

I would like the soft start and lower current draw, though.

 

[sberry]

This is living proof that anything can be further complicated if one tries hard enough.

 

[matt_i]

Why VFD?

They cost more than a single phase motor. VFD cause electrical noise and are hard on some motors. You cant really vary the speed too low due splash lube issues. I think a smart variable speed to respond to variable demand would have to be a homebrew. I dont know how and dont know a source.

I would like the soft start and lower current draw, though.

Its easy to set hard limits on the motor speed (Hz) via the VFD parameters.

As far as demand, in my mind a very simple setup is a "step" setup. When the pressure switch is closed, if the motor runs for X1 time and the timer T1 on delay is on, then you can ramp to speed step 2. If you run for X2 minutes and the T2 timer is on then you can ramp to step 3. Or set multiple pressure switches to associate greater pressure drop with more demand, but they have to be finely tuned...the lowest RPM is set by pump curves from the initial mfgr. There are plenty of projects to work on

 

[Ipassgas]

Thank you all for your insights and opinions.
As of now, I'm not going with this setup. The seller became flaky, and I'm too busy to try and chase down flaky.
But I did learn a lot about all that goes into changing 3 phase to 1 phase!

 

[sberry]

There are better ways of doing it than when I started and some service upgrades have been done but pocos don't really want large motors started and many of the guys I saw fart with this never did get anywhere and always seemed to be a piece short or got the great deal and now want to do a conversion more costly than simply buying something that can be plugged in to the wall. Needing not more than 50A circuit is another plus as is being able to use common cord and plugs.
If a real Bud was asking for an opinion would tell him that 5 hp 2 stage will do it all for most people. Less if you are not doing body work. Find something you can bring home and hook up for the cost of a piece of wire and a breaker, today, without having to do so much inventing unless that is the goal.

 

[86turbodsl]

Well, i can appreciate sberry's assertion that most people can do it with 5hp (true HP), but i would disagree with that on body work. Dad and I restored a couple of cars and he has a 6.5HP 2-stage and i could run that thing right out of air blasting and sanding. Just a data point. YMMV.

 

[arkieguide]

use 2 motors of same size and wiring, the driver motor hook to 220 v wires to it and the driven motor, hook the 3rd wire between the 2 motors. Tyhe drive motor makes the 3rd phase for the driven motor. good luck.