Hey Guys,
Need some help. I have a chance to pick up a very quiet compressor. The only problem is that it it has a 3hp 220v 3phase motor. Is it possible to convert this to 110v power?
-Rob

No. Better to have a 220 anyway. Do you have 2 spare or blank breakers in your panel?
If so, no problem.

P

I could probably create room in the panel to make it 220 single. Then what, run a 3 phase converter?

QUOTE (URY914 @ Dec 20 2004, 11:40 AM)

No. Better to have a 220 anyway. Do you have 2 spare or blank breakers in your panel? If so, no problem. P

Sort of.

Are you sure that it is only 220? Look for a box where the power cord goes. There may be a diagram on how to wire for 120 vs. 220. You can also look at the plate on the motor that gives the specs. If it only says 220 volts then that is what you have to supply. If it says 120/220 volts then there should be a way to switch wires around.

Having said that, I agree with Paul that 220 is better. If you have the extra breakers or spacers you should go that route.

-Jeff

QUOTE (rjkavanagh @ Dec 20 2004, 11:45 AM)

I could probably create room in the panel to make it 220 single. Then what, run a 3 phase converter?

No converter needed. It is two phase. You just have to run wiring from both breakers plus a neutral and ground to a new box and add a outlet that matches the plug on the compressor. The neutral is if there is a 120 requirement on the compressor in addition to the 220. I don't think that would be the case though.

The thing is that it has a 3 phase motor. 3 phase is industrial. Homes are only single phase. You can get a phase inverter but costly.
David

Hey Jeff, was just in your town yesterday. What a great day in SC.....
Anyway, The plate on the panel says only 3hp 220V 3phase. I can't get to the motor to see any other markings but I'm assuming that since it's a 3 phase motor, it would probably step to 440V if anything.
-Rob

Oops. I meant to say single phase. If you do have a three phase motor you will have to convert.

Sorry.

QUOTE (rjkavanagh @ Dec 20 2004, 12:03 PM)

Hey Jeff, was just in your town yesterday. What a great day in SC..... Anyway, The plate on the panel says only 3hp 220V 3phase. I can't get to the motor to see any other markings but I'm assuming that since it's a 3 phase motor, it would probably step to 440V if anything. -Rob

Yep. You would have to do a conversion. A friend of mine has a 120/220 motor on a honking big compressor. I was thinking that maybe you had the same.

Glad you enjoyed Santa Cruz. It has been beautiful the past few days. This morning I left a bright sunny sky only to hit dreary fog in San Jose.

-Jeff

A few options........


I bought a VFD (variable frequency drive, 220 single phase in..the output is a mimic'd 3 phase) for one motor of mine, but it does not start and stop as much as the compressor or have the same type of loads on it.

A rotary phase converter will work, expensive if you buy a new fully built unit, much, much cheaper if you build it yourself....you need a 3 phase motor larger than the one on the compressor, basicly you turn the large 3 phase motor into a generator, the new motor will run off of single phase and output 3 phase...yes, you use a motor to run another motor

there is also a static converter, but for high load items such as the compressor I don't think they work too well...

Here's a static converter http://www.use-enco.com/CGI/INSRIT?PMAKA=2...6&PARTPG=INLMK3
As Mike said, they aren't as good as a rotary converter and can get maybe 80% of the normal rated HP.

A 3 phase motor will run on single phase (at about 50% of the rated HP) but it won't start on single phase. There are capacitive starters for 3 phase motors that will allow it to start on single phase. Basically it jolts the additional leg with the discharge from a large capacator.

Check with Enco (maker of miling machines) sells them.

Thanks Guys, you've given me a ton of stuff to think about.
-Rob

Hey Rob, any chance you drive your car to work? Every once in a while I'll see a nice blue 914 pass by my job over on Lakeview Blvd ....

hold on now... are they asking for 3P 277, 240 or 208.

QUOTE (Mueller @ Dec 20 2004, 02:52 PM)

Hey Rob, any chance you drive your car to work? Every once in a while I'll see a nice blue 914 pass by my job over on Lakeview Blvd ....

QUOTE

Been driving the car from Fremont to work in Livermore almost every clear day since I got it a couple of months ago.
-Rob

QUOTE (carambola @ Dec 20 2004, 03:10 PM)

hold on now... are they asking for 3P 277, 240 or 208.

QUOTE

just checked and it says 3 phase 240V

master electrician hat on:

well 3 phase 240 volt is rare, and i doubt they built it that way, or at least the 240 3 phase we have in baltimore city( will explain at end of post ). but what it probably is a Y hook up, and you can get a transformer that will turn single phase 240 into 3 phase 240. not sure how much but i can find out. now some other option are getting the motor rewound, which would be cheaper than a new single phase motor. or as stated a rotary converter, and an electronic convertor, you would need lots oh money for a electronic one that could handle the start up surge. now rotary converters are not to cheap either, but you could build one for 50 bucks if you can find a motor thats rated at 125 % of the compressor motor, you would just need to shut it down manually and start it up with a couple of manual methods.
now if you are lucky that it is a Y set up its not difficult to get it running. but i would suggest rewinding the motor


now for the weird 240 volt we have here ( happens to be right around camdan yard ) there are three legs the center one to ground has no voltage, the 2 outer ones have 120 to ground, but if you go center ( nothing to ground ) to either outer leg ( 120 to ground ) you get 240, i have seen lots of people blow up tv's microwaves,a nd window ac's but thinking the center phase is a neutral and hooked a line to it and put 240 through what ever was pluged in. and yes this is in houses

master electrician hat off

I would think the cheapest thing to do would be to get biggest, baddest 220v single phase motor you can, and stick it on there. Then sell the 3 phase motor on ebay

We just went through this. Bought a big ass compressor. Realized it was 3 phase, landlord swore we only had single phase. We couldn't find any solutions that made real sense ($). Luckily the shop actually does have three phase, so no worries.

QUOTE (scott thacher @ Dec 20 2004, 11:27 PM)

well 3 phase 240 volt is rare

3-phase is common, in the US it's typically around 208 V phase-phase because of the 120 deg. difference between phases. I know someone who uses 3-phase converters because they were less expensive than having the power company bring 3-phase power to his shop (you can get 3-phase to your house if you're willing to pay for it, barring no zoning restrictions). In his case the motors are unique to the equipment (CNC tools) and can't be replaced with single-phase. For a compressor I'd swap it out with single-phase. You can get a 5 HP compressor motor for $110 at Harbor Freight.