460V Single Phase Air Compressor?

[kythri]

Local pawn shop has an 80 gallon IR air compressor, claiming a 230V/460V single phase motor.

They're closed today, so the only info I've got on it is from the CL ad:

https://corvallis.craigslist.org/tls/d/ir-ingersoll-rand-2-stage-80/6261338482.html

If anyone local (Lebanon, OR) is interested, obviously, there's the information.

I'm set on my compressor, but this just seemed wonky - is 460V single phase a thing?

I thought 230V/460V was 3-phase.

 

[larry_g]

Don't see any caps on the motor and those voltages are 3 phase. I've been in that shop.


lg
no neat sig line

 

[kythri]

I emailed to ask for a picture of the motor information plate. I saw the thing on the sidewalk driving by Friday afternoon, but didn't have time to stop to look at it.

If they don't respond to my email, I'll drive by and look at it after work tomorrow, but, yeah, it really seems that it's a 3-phase unit.

 

[MacMcMacmac]

Local pawn shop has an 80 gallon IR air compressor, claiming a 230V/460V single phase motor.

They're closed today, so the only info I've got on it is from the CL ad:

https://corvallis.craigslist.org/tls/d/ir-ingersoll-rand-2-stage-80/6261338482.html

If anyone local (Lebanon, OR) is interested, obviously, there's the information.

I'm set on my compressor, but this just seemed wonky - is 460V single phase a thing?

I thought 230V/460V was 3-phase.

Once in a rare while you will see small fractional hp single phase motors that are 460v or 575v, but usually they are part of a larger machine already hooked up to three phase, i.e. a 575v single phase fan motor on a large air dryer refrigeration circuit. Even this is rare, as usually there is a 110v or 220V step down transformer as part of the unit to provide voltage to the accessories.

 

[DavidB]

My money's on 3 phase as well. Like Larry said, no caps on the motor also indicates 3 phase.

 

[American Locomotive]

Don't see any caps on the motor and those voltages are 3 phase. I've been in that shop.


lg
no neat sig line

Look how large the junction box on the motor is. 10-15HP single-phase motors usually contain their capacitors in a large box like that.

Also note it appears to have a standard Lowes/Home-Depot style NEMA 6-50 plug on the end.

 

[sweetk30]

that unit with 10hp motor gets a mag starter in that huge box .

I have a unit like that t30 pump on my setup at my home shop with a 5hp and love it . at the 5hp speed it sounds like a old DETROIT DIESEL at idle .

my buddy who use to be a ir engineer told me don't waste your time on rebuilding the newer black pumps NOT made in the use . there basically use it and toss it when done.

 

[kythri]

I'm working a later shift today, so I swung by and snagged a couple pictures:

 

[American Locomotive]

Very strange motor!

 

[larry_g]

Well hell, I'm going to have to stop assuming no cap housings=3 phase.

lg
no neat sig line

 

[WittHay]

I could be wrong, but i think its a 3-phase motor designed to run single-phase on 3-phase power. To run on 230 it would be connected to just one line of 3-phase, to run on 460 it would connect to two lines

There is 277 volt single phase fluorescent and metal halide lighting that works on 1 leg of 480 volt 3 phase power

Up here, you have to watch when you buy used commercial lighting, as a lot of it is 347 volt single phase for use with 600 volt 3 phase power. I have seen 575 volt single phase motors

 

[454ragtop]

I could be wrong, but i think its a 3-phase motor designed to run single-phase on 3-phase power. To run on 230 it would be connected to just one line of 3-phase, to run on 460 it would connect to two lines

There is 277 volt single phase fluorescent and metal halide lighting that works on 1 leg of 480 volt 3 phase power

Up here, you have to watch when you buy used commercial lighting, as a lot of it is 347 volt single phase for use with 600 volt 3 phase power. I have seen 575 volt single phase motors

Huh? It's a regular single phase motor, caps are in that box on the side of the motor.

 

[nh_yota]

460v (really 480v) single phase motors are rare but they are generally used in rural areas where three phase power isn't available and there is only one leg of a high voltage line running down the road.

 

[American Locomotive]

Well hell, I'm going to have to stop assuming no cap housings=3 phase.

lg
no neat sig line

It does have a cap housing. The give away is the gigantic junction box on the side. It's far larger than a motor junction box. They stuff all the caps in there.

I could be wrong, but i think its a 3-phase motor designed to run single-phase on 3-phase power. To run on 230 it would be connected to just one line of 3-phase, to run on 460 it would connect to two lines

No. 460v 3-phase is 460v line-to-line, 230v 3-phase is 230v line-to-line. This motor just gets connected across two phases of the 3 phase service.

 

[WittHay]

Thanks American Locomotive for the clarification, I had a second look at the picture and my wording was not right. It is a single phase motor just like the label states

 

[kythri]

So, to run it at 460V, you have to have three-phase power, but you're just connecting two single-phases of the three-phase?

Could you conceivably wire in two single-phase circuits into it and power it at 460V? Do quad-gang breakers exist?

Just curious how it all works.

ETA: I guess quad-gang breakers are a thing:

http://www.homedepot.com/p/Eaton-Tw...-Quadplex-Circuit-Breaker-BQC240240/100557207

 

[nh_yota]

Why not just wire it at 230V? I bet it's wired for 230V anyway.

 

[The Tool Tyrant]

Very strange motor!

Well hell, I'm going to have to stop assuming no cap housings=3 phase.

lg
no neat sig line

I could be wrong, but i think its a 3-phase motor designed to run single-phase on 3-phase power. To run on 230 it would be connected to just one line of 3-phase, to run on 460 it would connect to two lines

There is 277 volt single phase fluorescent and metal halide lighting that works on 1 leg of 480 volt 3 phase power

Up here, you have to watch when you buy used commercial lighting, as a lot of it is 347 volt single phase for use with 600 volt 3 phase power. I have seen 575 volt single phase motors

Below is from the century website, so it is indeed single phase.


Single Phase Capacitor Start Capacitor Run
5 1745 230 22.0 184T V209 1-1/8” x 2-7/8” F REV 15.0 82.0 5,$
7 1⁄2 1750 230/460 32.0/16.0 215T V305 1-3/8” x 3-1/2” B REV 17.3 86.0 5,80,$
10 1750 230/460 38.0/19.0 215T V303 1-3/8” x 3-1/2” F REV 17.9 86.5 5,80,$

 

[Matt Matt]

So, to run it at 460V, you have to have three-phase power, but you're just connecting two single-phases of the three-phase?

Could you conceivably wire in two single-phase circuits into it and power it at 460V? Do quad-gang breakers exist?

Just curious how it all works.

ETA: I guess quad-gang breakers are a thing:

http://www.homedepot.com/p/Eaton-Tw...-Quadplex-Circuit-Breaker-BQC240240/100557207

Under the motor tag picture there is a connection tag diagram that you're only half showing. I can see clearly there is a reverse swap (8 and 5) for low-voltage. Can you show us the rest of that picture. It is clearly a capacitor start or has run capacitors slightly shifting some of the field windings to provide start direction.

I am not exactly sure why you want to run this on 460 V unless of course you have 460 V. The link you provided 2=>40amp 2 pole, In no way does this double the voltage, and you shouldn't really use mini breakers in a motor circuit. If you have 230 V, you will need a step up transformer to wire this at 460 V. But, then you also have to deal with the contactor. There's a light switch on the bottom of the starter box. The starter coil is probably 230 V. Good chance be this came out of a single phase shop that only had 230 V. They probably have a 5-50 welding plug on the end of it. The previous owner was probably powering it with 50 amps at 230 v single phase. I am guessing that A.O. Smith(The motor manufacturer), just took the design of a 115-230 Volt 4 pole motor and applied it to the 7.5 HP situation. But it would've been silly for A.O. Smith to wire it for 115–230 V. The 115 V would have 64 A FLA. I don't think I've seen a 75–80amp 115 V, single phase breaker. (The wiring and plug would be an absolute nightmare.) The next situation is, if One were to want to hook this up to 460 V single phase, they would probably have to swap out the run capacitors for 600v caps. I have a feeling the run capacitors only have a rating of 370–440 V.

 

[EOC_Jason]

So, to run it at 460V, you have to have three-phase power, but you're just connecting two single-phases of the three-phase?

Could you conceivably wire in two single-phase circuits into it and power it at 460V? Do quad-gang breakers exist?

Just curious how it all works.

No, more circuits does not equal higher voltage.

Your residential 120/240v power looks like the black & maroon waveforms in the graph below. They are just 180-degrees apart from each other, that's how you get your 240v line-to-line...

 

[kythri]

I'll try to snag another picture.

That said, ultimately, I'm just curious at this point - I'm not interested in buying this compressor, just trying to figure out how one gets 460V single-phase.

 

[Matt Matt]

I'll try to snag another picture.

That said, ultimately, I'm just curious at this point - I'm not interested in buying this compressor, just trying to figure out how one gets 460V single-phase.

To get single phase 460 which has two hot separated by 180°, you would need a step up transformer on a 230 V single phase system or;

On a three-phase 480 v system you just use two of the three legs.

https://ctlsys.com/support/electrical_service_types_and_voltages/

 

[EOC_Jason]

That said, ultimately, I'm just curious at this point - I'm not interested in buying this compressor, just trying to figure out how one gets 460V single-phase.

It would be in a commercial facility that has 480V 3-phase... You are only hooking up two of the legs... It's just added flexibility in the design but I would bet 95% of the installs are for 240V single phase.

They make welders with similar configurations.

 

[Dozerhand]

I had a single phase Miller Dial-Arc welder that was hardwired to an asphalt plant to run on 460. I had to swap around some buss bars to make it run on 230.

 

[Matt Matt]

It would be in a commercial facility that has 480V 3-phase... You are only hooking up two of the legs... It's just added flexibility in the design but I would bet 95% of the installs are for 240V single phase.

They make welders with similar configurations.

It would not need to be a commercial shop. But it would absolutely silly for any one to "want" to convert it without a commercial shop.

If it came out of a commercial shop, it would have been three-phase. A 7.5 hp motor at 230v would have a FLA of 21A ish, and at 460v 10.5A ish and 600v 8.4A ish. So, at 460,600v you would only need 14g wire. At 600v, a motor is about 1-1.2A per hp.

 

[A_Pmech]

480V and 600V single phase motors are available to at least 100 HP. Fairly uncommon these days, but still used in rural locations. I bet that motor is expensive.

 

[EOC_Jason]

It would not need to be a commercial shop. But it would absolutely silly for any one to "want" to convert it without a commercial shop.

If it came out of a commercial shop, it would have been three-phase. A 7.5 hp motor at 230v would have a FLA of 21A ish, and at 460v 10.5A ish and 600v 8.4A ish. So, at 460,600v you would only need 14g wire. At 600v, a motor is about 1-1.2A per hp.

What I meant was that about the only place you will typically see 480v is in a commercial facility (as opposed to residential that is only 240v).

After doing a little more reading (and what Pmech just posed) it looks like they have (or had) 480v single-phase in rural locations (farmers/ranchers). Though I'm sure these days they would set them up with proper 3-phase if needed.