Is a phase converter bad for a motor?

[DavesGarage]

I am close to purchasing an Eaton compressor but I am stuck on deciding on 3 phase or single phase. I do have 3 phase on my home but the wife has been talking about moving the last few months. Is it beneficial for me to buy a 3 phase and benefit from cheaper operating costs and easier operating motor or do I go with a single phase because of the unknown of moving to a home that more than likely only has single phase?
If I do go with the 3 phase and end up moving is a phase converter on a 3 phase motor altered to single phase bad for the motor? Will it still operate efficiently like a 3 phase or will it be just like a single phase? A phase converter is $680 so it will be a toss up also whether to replace the motor or go phase converter. Thanks for any info!

 

[A_Pmech]

A properly sized and balanced phase converter is not bad for the load motor. Many machine shops and industrial outposts are set up in locations without access to 3-phase power.

However, it is rather redundant to operate a converter just for an air compressor, especially when a new single-phase compressor is an option. If you plan on moving, I would purchase a single-phase machine.

 

[Falcon67]

Agree with Pmech. For a compressor, a single phase 240V would be a better choice. I run a 240V-3 phase converter on my 1HP 3 phase mill/drill and the converter is a great item for that machine. My 2 HP converter was right at $200. I would use a converter on a mill, lathe, drill press, etc - but not so much on a compressor unless it was something like a medium size upright 3-5HP 3phase compressor and dirt cheap (< $100) or free.

 

[larry_g]

As I understand phase converters they are not the best for high load situations. A compressor is running loaded a large portion of the time and there fore requires an oversized converter. I have been running my machines on a rotary for better than 10 years so they do work quite well. I'm just not sure that running a compressor is recommended.

lg
no neat sig line

 

[theoldwizard1]

If the motor on the compressor is under 7hp, you can remove the 3ph unit and replace it with a single phase 240V unit. Selling the 3ph motor should pay most of the new motor.

A lot less than a phase converter !

 

[930dreamer]

I run my Champion 5hp on a 10hp rotary converter.

 

[NASTYZEN]

1 phase compressor is the common way to go. You can plug it anywhere.Sell it to anyone.
You would have to keep your phase converter running all day waiting for the compressor to kick in now and again. Not economical.There also noisy.
Or turn on and off the converter all day...
In my opinion, I don't think you have significant power savings with a 5hp compressor running on 3 phase in the long run. You have to draw much more power to make it show.

I have a 45hp Rotary phase converter that shakes the building when I turn it on.
It powers a cnc 5hp lathe , cnc 5hp mill and a 5hp angle roll, all at the same time.
My house energy bill is by far more expensive than the shops.

 

[Todd.Brock]

They can't seem to give away 3 phase motors around here on CL... If you did buy single phase and regret it or end up staying you could re power with three phase and sell the single phase compressor motor on CL.. My personal opinion Is to go 1 phase... She may stop the moving talk for a while, but it will come back...

 

[DavesGarage]

Single phase it is then. Thanks for the good info guys!

 

[wyliesdiesels]

I am close to purchasing an Eaton compressor but I am stuck on deciding on 3 phase or single phase. I do have 3 phase on my home but the wife has been talking about moving the last few months. Is it beneficial for me to buy a 3 phase and benefit from cheaper operating costs and easier operating motor or do I go with a single phase because of the unknown of moving to a home that more than likely only has single phase?
If I do go with the 3 phase and end up moving is a phase converter on a 3 phase motor altered to single phase bad for the motor? Will it still operate efficiently like a 3 phase or will it be just like a single phase? A phase converter is $680 so it will be a toss up also whether to replace the motor or go phase converter. Thanks for any info!

3-phase is NOT cheaper to operate. This is because PoCos not only charge for total usage like single phase service charges but also TOU and KW demand charges for 3-phase service. However, 3-phase motors are more efficient.

If u ever do any wiring in your home make sure to familarize yourself with 240v/120v Delta 3-phase which has a "stinger" leg!!

 

[MackMan]

Just stumbled into this on a search. I am buying a commercial garage that does not have 3-phase power, but the seller is leaving me a 15HP 3-phase Champion compressor that he says worked when he bought it but he hasn't been able to hook it up. He is also leaving me an 80 gallon single phase Kobalt compressor so I have a compressor.

Is it worthwhile to get a transformer for the 15HP compressor or would it be better to just sell the compressor? A new 15HP Champion is $6,000 but no idea what a used one that may or may not work is worth.

 

[A_Pmech]

Is it worthwhile to get a transformer for the 15HP compressor or would it be better to just sell the compressor? A new 15HP Champion is $6,000 but no idea what a used one that may or may not work is worth.

The questions to think about are:

1) Do you need 15 HP worth of air?

2) Can your existing singe-phase service provide the necessary power to run it though a phase converter?

 

[MackMan]

The questions to think about are:

1) Do you need 15 HP worth of air?

2) Can your existing singe-phase service provide the necessary power to run it though a phase converter?

1) Almost certainly not, my 30 gal Craftsman has been fine so far, and I will have a 4.5HP 80 gal Kobalt with the building. This was more a "because it's there and free" type of option, and would be a substantial permanent upgrade to the building.

2) No idea.

So on top of that, any idea how I would value a used compressor that I can't verify the function of without 3-phase? A new one is ~$6,000, so I'd think a fully functioning one would be worth at least 50% of that, but I can't verify function. Thoughts?

 

[A_Pmech]

Because it's there and free probably isn't the best way to look at it. To get that machine wired up and running in a single-phase shop (assuming sufficient power is available) would be a $1,500 to $7,500 proposition depending on how much of the wiring and equipment you build yourself.

So on top of that, any idea how I would value a used compressor that I can't verify the function of without 3-phase? A new one is ~$6,000, so I'd think a fully functioning one would be worth at least 50% of that, but I can't verify function. Thoughts?

From the perspective of a business owner who uses industrial reciprocating compressors, I won't pay more than 15% of new for a used one in good working order. There are just too many nice compressors out there to pay more than that. Most medium and large companies buy them new.

 

[MackMan]

Because it's there and free probably isn't the best way to look at it. To get that machine wired up and running in a single-phase shop (assuming sufficient power is available) would be a $1,500 to $7,500 proposition depending on how much of the wiring and equipment you build yourself.



From the perspective of a business owner who uses industrial reciprocating compressors, I won't pay more than 15% of new for a used one in good working order. There are just too many nice compressors out there to pay more than that. Most medium and large companies buy them new.

Thanks for the feedback, I haven't looked into the building power supply at all (don't go to closing until tomorrow), and didn't know details on the compressor until last night, so just trying to figure out a plan. My understanding is the PO purchased it with the intention of wiring it to the shop, but found the transformer to be too expensive at the time so he bought the Kobalt instead. Sounds like that's going to be the best option for me as well.

 

[wyliesdiesels]

Just stumbled into this on a search. I am buying a commercial garage that does not have 3-phase power, but the seller is leaving me a 15HP 3-phase Champion compressor that he says worked when he bought it but he hasn't been able to hook it up. He is also leaving me an 80 gallon single phase Kobalt compressor so I have a compressor.

Is it worthwhile to get a transformerfor the 15HP compressor or would it be better to just sell the compressor? A new 15HP Champion is $6,000 but no idea what a used one that may or may not work is worth.

What voltage is the compressor? If its the same as the building service then a transformer is NOT what you need. U need a phase converter such as a rotary phase converter, that makes 3-phase power with single phase power input. And if the compressor is a different voltage then u will need a phase converter AND a transformer!! Rotary phase converters can be built for relatively cheap but transformers can be expensive unless a good deal can be found on a used one!