Got a 3 phase electrical question

Chevy1925

Chevy1925

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So I've got a 5 hp 3 phase compressor sitting at our shop that I have acquired. It's and old "slow pumper" and the plan is to bring it home and use at my house.

Here's the issue. Obviously I have no 3 phase power in a sub division. So I can buy a new motor that's a single phase 5hp or run a rotary phase converter. So far a rotary phase converter seems to be the cheaper route but I'm unsure of what size idler motor Id need to run my compressor correctly. Not planning on adding any more 3 phase at this house, not enough room for more shop toys lol.


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bobxr50

bobxr50

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I have install single phase to three phase systems at my work for sewer lift stations that are remote areas no 3 phase power.
This is what I have found out in my experience...
Rotary phase converters (single phase motor) work but they take up space and are not efficient.
Capacitor style phase converters work with the correct style motor. But need to understand if you blow a capacitor. I install these the most.
Then if you can find a cheap VFD to run the motor that is the most efficient way. But they cost the most.

If I was going to use this air compressor I would replace the 3 phase motor with a single phase and be done with it. Sell the 3 phase motor.
 
henery97

henery97

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Swapping the compressor to a single phase would probably be the best route. That or a VFD, but you need to oversize the vfd bc of the single phase input.
 
duratothemax

duratothemax

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I agree with everyone else, cheapest option is to swap to a single phase motor. 5hp single phase air compressor duty motors are dime a dozen from places like Northern etc.

You'd need a pretty large rotary converter, or a decent sized VFD to run a 5hp air compressor. Both of which are more expensive than a new 5hp single phase comrpessor motor.
 
Chevy1925

Chevy1925

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duratothemax said:
I agree with everyone else, cheapest option is to swap to a single phase motor. 5hp single phase air compressor duty motors are dime a dozen from places like Northern etc.

You'd need a pretty large rotary converter, or a decent sized VFD to run a 5hp air compressor. Both of which are more expensive than a new 5hp single phase comrpessor motor.
Click to expand...

I wish they were easy to come by. this is a 184t frame, 1740rpm. cheapest i can find is ebay for 360 bucks. been scowering craigslist for the last few months and only came across one motor that was sold by the time i called.

i might see if i can modify the mount to allow a different frame motor to fit but ill need to buy a new pully as well since this is a 1 1/8" shaft and most out there are 7/8". no biggy there though
 
duratothemax

duratothemax

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Chevy1925 said:
I wish they were easy to come by. this is a 184t frame, 1740rpm. cheapest i can find is ebay for 360 bucks. been scowering craigslist for the last few months and only came across one motor that was sold by the time i called.

i might see if i can modify the mount to allow a different frame motor to fit but ill need to buy a new pully as well since this is a 1 1/8" shaft and most out there are 7/8". no biggy there though
Click to expand...

damn...copper must have gone up! I just looked around for 10 minutes and the cheapest 184t-frame single phase 5hp motor I found was like $320.

The largest single-phase-input VFD can only drive up to a 3hp motor.

So that leaves you with a static phase converter (shitty, basically just a capacitor that discharges and generates the 3rd leg for a second or so to get the motor started...but even once the motor gets going its only going to produce 2/3 the rated HP when run on single phase.

IMO, I would just find a NEMA 56-frame motor and re-drill the motor base or compressor base.
 
MACKIN

MACKIN

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What is the voltage on the 3 phase 220 or 480? I'm no electrician but I know there is a way to do 3 phase 220 volt.
 
duratothemax

duratothemax

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MACKIN said:
What is the voltage on the 3 phase 220 or 480? I'm no electrician but I know there is a way to do 3 phase 220 volt.
Click to expand...

Yes, but its still a 3-pole (3 phase) motor...you cant just run a 3-phase motor on single phase, even if the voltages are the same.
 
Chevy1925

Chevy1925

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duratothemax said:
damn...copper must have gone up! I just looked around for 10 minutes and the cheapest 184t-frame single phase 5hp motor I found was like $320.

The largest single-phase-input VFD can only drive up to a 3hp motor.

So that leaves you with a static phase converter (shitty, basically just a capacitor that discharges and generates the 3rd leg for a second or so to get the motor started...but even once the motor gets going its only going to produce 2/3 the rated HP when run on single phase.

IMO, I would just find a NEMA 56-frame motor and re-drill the motor base or compressor base.
Click to expand...

thats what im thinkin too, redrill, throw a pulley on and go. cheaper to replace down the road too

duratothemax said:
http://www.ebay.com/itm/LEESON-MOTO...197?pt=LH_DefaultDomain_0&hash=item19e55d3c7d

offer them $250?? It doesnt specifically say "single phase", but its got a large capacitor on it, and Ive never seen a 3-phase motor with a start/run cap...so its gotta be single phase.
Click to expand...

id have to redrill that bad boy and buy a new pully, plus shipping id be damn close to just buying a 184t frame new one

duratothemax said:
http://www.ebay.com/itm/Baldor-5-HP...e&pid=100005&rk=4&rkt=6&sd=111222275197&rt=nc
Click to expand...

plus 100 bucks to ship. bastards


I think what ill do is get the Norther Tool 5 hp one, even though its 3450rpm (not 1700 like i need), ill pulley it down and be good to go.
 
duratothemax

duratothemax

<--- slippery roads
Aug 28, 2006
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Wyoming
Chevy1925 said:
id have to redrill that bad boy and buy a new pully, plus shipping id be damn close to just buying a 184t frame new one
Click to expand...

isnt that one a 184 frame? Its got "184" in the part number, so I assume its 184 frame.

Chevy1925 said:
I think what ill do is get the Norther Tool 5 hp one, even though its 3450rpm (not 1700 like i need), ill pulley it down and be good to go.
Click to expand...

Yeah 5hp 3450rpm single phase "compressor duty" motors are comparatively cheap, because thats what all the low/midrange compressors nowadays use. Probably the best bet. :(
 
MACKIN

MACKIN

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Heres what I don't know! :D


This building I'm in never had 3 phase heavy power (480 v) . I needed it so I had it installed. The old system is back feed with a step down transformer. Now what was in this building prior to me was a industrial electric motor rebuilding rewinding company.

They had to test run every motor they repaired and I recall him telling me there is a way to wire 3 phase . It was some time ago I just recall had something to do with the neutral wire to make it work. ?
 
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