Change a 3 phase compressor to single?

[jayoldschool]

I think this is a good deal, but how to get it to run at my house? I have a dedicated 220 in the garage...

"Ingersoll Rand 7.5 HP late model 2-stage compressor. Power required is 550v 3 phase. A heavy duty compressor at an incredible price. We are liquidating our factory.Please note - the compressor is located in the basement and must be removed by the purchaser."

They are asking $500.

 

[rsanter]

that is a whole lot of compressor
if you have the need and it is in good shape then that may be the deal for you
because of the odd voltage I would look at a motor swap but price the motor first because they can get expensive.

also note the location bieng the basement and thet you have to remove it. be sure you look and see what it will take to remove it. what about disconnecting it? some places for liability reasons will require you have a certified electrician do it.

bob

 

[PowerDubs]

Where is it located? If you don't take it, I will

 

[Elroy]

That is one hell of a deal but you got two small problems. The first is getting it out of the basement. Those things are HEAVY. Like 700 pounds heavy.

Then you have to wire it run off 220 volt single phase which is going to require a motor change. That is not going to be cheap.

So on the face of it, good deal with a large expensive pain in the *** attached. Elroy would pass

if you could avoid the motor change it might be worth the effort to procure. Combine the motor change with the location

forget it

 

[jayoldschool]

Moving it is not a problem. I handle old coke machines and juke boxes by myself with a fridge cart. A good cart, three strong guys with straps, and it will be up and out.

Tell me more about a motor swap...

Or, can I get three phase to my house? The line passes right in front of my place...

 

[jay50]

Moving it is not a problem. I handle old coke machines and juke boxes by myself with a fridge cart. A good cart, three strong guys with straps, and it will be up and out.

Tell me more about a motor swap...

Or, can I get three phase to my house? The line passes right in front of my place...

Check Northern Tool for an idea of motor price. I looked at a similair compressor as yours but passed on it after pricing the motor I needed at $450

 

[usa#1]

Three phase power is typically a commercial thing, not for a home residence. Why not check out the age of the compressor and condition, cost of an identical new one and purchase it on that basis. If its in good shape $500 is a good price. You could then start looking for a deal on a new or used motor. If you can't find a motor for a good price, then just sell the compressor to a business that has 3 phase power and apply the profit toward a similar unit that comes with a single phase motor.

 

[PCW]

Tell me more about a motor swap...

Eaton Compressors have great Baldor motors. I am ordering an Eaton Compressor tomorrow.

http://www.eatoncompressor.com/motors.html

PCW

 

[rsanter]

you have 2 problems with that motor
1 is that it is 550v
2 is that it is 3phase

the 3 phase is easy to deal with because you can get a phase converter or better yet a VFD off ebay for a reasonable price of you are patient

the bigger problem is the 550v. you can get a transformer to step up the voltage but those are not cheap. some motors can be rewired to multiple voltages but I suspect that the 550v cannot be rewired to run on the 220. if it can you are on easy street.

you may want to look at used motors to see what you can find

bob

 

[rockvr4]

the 3 phase is easy to deal with because you can get a phase converter or better yet a VFD off ebay for a reasonable price of you are patient


bob

Bob,

Can you explain the VFD positives and negatives over a phase converter. I was going to hook up my old Delta drill press 3 phase and was initially looking at a phase converter. Thanks

Sorry for the thread jack

 

[Torque1st]

To run a 7.5HP compressor a person is looking at:
-20HP phase converter $$$$
-7.5 single phase or 15HP? 3-phase VFD $$$$$$$$$$$$$
-7.5HP single phase motor, plus new starter switch and 40A power draw, $$$$$$$$

PASS on the unit.

Bob,

Sorry for the thread jack

You can find all kinds of explanations at:
http://www.practicalmachinist.com/vb/forumdisplay.php?f=11

 

[rsanter]

there are a couple of different phase converers.

1 rotary phase converter. this type creates true 3phase power with little to no losses to the rated HP of your driven device (the compressor in this case). this is also going to take the most room and is expensive.
the rotary phase converter consists of a 3phase motor with some capacitors and other circutry to take the 2 phases and fill in the third phase. the losses are adsorbed in the phase converter motor.
you will need about a 12-14 HP 3phase motor to create a rotary phase converter for a 7hp driven motor
if you buy one it will generally cost $100 per HP

solid state phase converter.
a solid state phase converter is smaller and much less expensive but you will lose about 30% of the rated HP of your driven device (the compressor in this case). with a compresor this can cause a problem getting the compressor pump going when the compressor goes to restart (already have some pressure in the tank). these work ok on things like mills and lathes because you can start them under no load conditions and then when operating them you will have to take lighter cuts than max capacity.
a solid state converter consistst of some capacitors and a starting circut so that the driven motor will get going and run by taking the 2 phases and filling in the third phase.

VFD (variable frequency drive)
a VFD is a solid state device that takes in single or three phase AC electricity in and converts it to DC and then will electroncally convert it into three phase electricity to feed into the driven motor. the nice thing is that the VFD will have very little losses of power in the driven motor and it will also give you the ability to vary the speed of the driven motor by varying the frequency of the output electricity so there is little to no loss in rated HP of the driven motor even when you turn the speed down.
in the case of an air compressor there is usually no need to vary the motor speed but the real benifit is the ability to convert the single phase to 3phase with little losses and at the same time you also gain the 'soft start' feature which ramps the motor speed up instead of giving it the sudden shock of applying full electricity in one shot.
these will often cost $75 to $150 per HP but you can often find bargains on ebay

I hope I made this understandable

bob

 

[A_Pmech]

Depends on how much you can beat him down. Never know...

If you know how to scrounge, you can get a 7.5HP single-phase motor on that thing for $200.

Never buy new motors from the factory! There are ALL KINDS of motors, NOS, new, used, floating around.

 

[rsanter]

look at the factory webside and see what the specs are on that unit if it has cone with a 220 single phase motor

bob

 

[krooser]

You should be able to trade-in the 3 phase at local motor shop for the correct motor. I bought a used 5HP single phase for $150.00 plus my burned out trade. A 7.5 might be $100.00 more... call around.

Looks a good compressor to me... a comparable new unit would be over $2K....

 

[3/8"indestro]

what's the pump model number? looks like a 2475 pump.you can run them as a 5 horse,which would be cheaper.Baldor motors can be had from e-bay for $300 shipped.offer him $400 + the $300 cost of motor and you have a nice compressor for $700.take the pump,motor,wiring,piping out to lighten it coming from the basement.you will be replacing the motor anyway,so why not.

 

[Rolling_Thunder]

Here's a motor for it! Id do it for that price! a couple cases of beer and a few big friends and its easy to move! Replace with single phase and possibly a new relay for the phase 1 setup and your good to go!

gpto www.grainger.com type in search "compressor 7/5!

 

[jayoldschool]

Got a link for that motor? I can't find it on their site...

 

[Bigrhamr]

A rotary phase converter is easy to build and cheap if you scrounge parts. I've got about $100 in capacitors and switches for my 7-1/2 hp RPC plus the motor which was another 100 at an electrical salvage place. The downside to an RPC on a compressor is it has to sit there and run if you want three phase available to start the compressor. It doesn't draw much juice at idle but it's still kind of pointless unless you have other three phase stuff to run off it. A static convertor on a compressor IMO would be a bad idea, cuts the power too much and compressors start kind of hard anyway. And, the 550v is probably going to make that motor a no go anyway. Then you have the single phase options. A real 7-1/2 horse single ph like what that compressor will need is a hard starting juice sucking beast which will probably dim your lights on startup. Don't confuse that 7-1/2 horse with one you'll find at Harbor Freight which is a toy in comparison. I'd say your most practical option is to go with a 5hp single ph and run it a little slower if need be. I did that on a big old Devilbiss 2 stage that had a 10 hp 3 phase on it. I think the only concern doing that is lubrication, it may need a minimum RPM to lube properly. IR can tell you easily if you give them the model #.

 

[Rolling_Thunder]

Never mind I was looking at the wrong area for the price! Its $766!

 

[fabman_52]

The only 2 things you really have to worry about is the motor rpm and pulley size, you can get a motor cheap enough on Craigs-List I see them sometimes as low as 25 bucks, Just make sure the rpm and pulley are correct. Hopefully you will be able to use your pulley on the new motor.

I recently did a motor swap on one of my compressors, the pulley hole size was to small on my pulley, so I took it to work and my buddy in the machine shop was able to make it work. It has a tapered hole so make sure they know what they are doing.

If you shop smart you should be able to do it all really cheap, under 200.00 for sure. which with the 500.00 for the compressor is still a super deal!

George.

 

[stinkythings.com]

You can visit www.dealerselectric.com for VFD options they have great customer service. I would keep the 3 phase motor if you can. I just bought a 10 HP VFD to run an 8000lb. die cutting press I have in my garage. They were extremely helpful, HAROLD is the person I spoke with. He went over and above for my situation.You will also find them on Ebay with an impeccable selling record.

 

[buening]

I will second the suggestion of taking the pump and motor off before moving it! These things are extremely top heavy and a dolly doesn't help moving something that is top heavy, especially up a set of stairs

I agree, check your local electrical motor shop for units they sell (either new or rebuilt) and ask if they will give you any thing for your 3-phase in trade. If anything, check Ebay or Craigslist for motors

 

[pblanton]

A rotary phase converter is easy to build and cheap if you scrounge parts. I've got about $100 in capacitors and switches for my 7-1/2 hp RPC plus the motor which was another 100 at an electrical salvage place. The downside to an RPC on a compressor is it has to sit there and run if you want three phase available to start the compressor. It doesn't draw much juice at idle but it's still kind of pointless unless you have other three phase stuff to run off it. A static convertor on a compressor IMO would be a bad idea, cuts the power too much and compressors start kind of hard anyway. And, the 550v is probably going to make that motor a no go anyway. Then you have the single phase options. A real 7-1/2 horse single ph like what that compressor will need is a hard starting juice sucking beast which will probably dim your lights on startup. Don't confuse that 7-1/2 horse with one you'll find at Harbor Freight which is a toy in comparison. I'd say your most practical option is to go with a 5hp single ph and run it a little slower if need be. I did that on a big old Devilbiss 2 stage that had a 10 hp 3 phase on it. I think the only concern doing that is lubrication, it may need a minimum RPM to lube properly. IR can tell you easily if you give them the model #.

I know this is an old thread but I have the same issue right now, except on a two-post 9000# lift that is three-phase, and I just had to write to tell you what a well crafted, well considered post this is. You cover all of the bases with no extranneous cruft. Congratulations and thanks!