Single phase motor on 3 phase power

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Brian.Evans

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I have a great deal on a 2hp 1800 rpm motor, but it is single phase. I can't find a decently priced single phase in/single phase out VFD. Will a single phase motor run on three phase?
 
medicevans said:
I have a great deal on a 2hp 1800 rpm motor, but it is single phase.

I can't find a decently priced single phase in/single phase out VFD.

Will a single phase motor run on three phase?
Click to expand...

I can't find a decently priced single phase in/single phase out VFD.
It doesn't exist, there is no point.


Will a single phase motor run on three phase
No

If you want to use a VFD, you need a 3 phase motor.
I find then cheap and easy to find on Ebay, shipping is my major catch, but in USA you should have less trouble.
 
Ok. thanks Sam.

How would I run speed control on a single phase, or is it not possible?
 
That's what the VFD does, turns your single phase into 3 phase, allowing you to vary the frequency, thus the RPM.

Must have a 3 phase motor.
 
medicevans said:
Ok. thanks Sam.

How would I run speed control on a single phase, or is it not possible?
Click to expand...


single phase into a VFD and a 3 phase motor

single phase into a DC controller with a DC motor


Step pulleys
This is not as cheap as you may think
Maska cast steel pulleys are good and well balanced $75 EACH here
Shaft, bearings, belt

It all adds up to about 1/2 the price of a KBAC-27D

I like direct drive, no belts and a VFD for about 150 to 200 over the price of the step pulleys with much finer control
 
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^
^
best argument for VFD over pulleys I've heard to date.
 
Another explanation why a single phase AC motor won't work with variable speed. They make speed potentiometers. If used on a single phase AC motor it will give you variable speed, but will burn up the motor AND the power of the motor is reduced as the speed drops.
 
Look at eBay for 3 phase motors. Learn to decipher the date codes since new old stock can be as old as 12 years old. I found this out after inquiring.

For example, on Baldor motors the serial number: first 4 numbers after letter are YYMM.
 
Look at eBay for 3 phase motors. Learn to decipher the date codes since new old stock can be as old as 12 years old. I found this out after inquiring.

For example, on Baldor motors the serial number: first 4 numbers after letter are YYMM.
 
I've found that some motor shops and used tool stores have an excess of 3ph motors they will sell for really cheap or give away. At least here, that is.

I just got a free 1hp 3ph motor, and not long ago got a 7.5hp 3ph for $100.
 
junkyards near industrial areas often have loads of burnt out 3 phase motors. You can grab them for next to nothing. Then take them to the motor shop and have them rewound. Much much cheaper than buying them new.
 
Junkyards often have salvage 3 phase motors in good running condition, too. I got the 3hp TEFC for my hammer in new condition for $65 from a junkyard. I got a single phase TEFC Baldor 5hp for $100 out of scrap machinery locally, too.
 
But what do you do with a single phase motor? I want variable speed.

I really am serious though, why do you do with that great big single phase?
 
Pulleys.

Or use a router speed control if it will work with your motor.
My limited experience shows you get about zero power that way though.
I tried it on a couple of bench grinders, then promptly returned the controller.

Otherwise, for proper Variable speed you need a 3 phase motor and VFD, or a DC motor and controller.

Unless you really have some skills, then you could invent a transmission that turns a constant input RPM into a variable output RPM.
One of the other options is far more cost effective though.
 
My mom's sewing machine has a foot pedal connected to some transmission gizmo on the motor and allows for speed control. No idea about torque/rpm stuff with that, but it's pretty neat.

I'll go look into it...
 
medicevans said:
I have a great deal on a 2hp 1800 rpm motor, but it is single phase. I can't find a decently priced single phase in/single phase out VFD. Will a single phase motor run on three phase?
Click to expand...

I guess I am confused. Are you saying that you currently have access to 3 phase power in your shop? If that is the case then you can use single or three phase motor. If you have a good deal on a 2hp single phase motor then get it and use step pullies. No, you can't fine tune them like you can with a VFD, but they work well with step pullies. The $75 pullies may be the bees knees, but the $10 ones from Ace hardware work well too. I use them and haven't had any issues at all.

I was given a 2hp pool pump motor and use it with step pullies. I think I have about $70 in my step pully setup and love it. If the motor is cheap, go for it. If you don't like it you can always sell it on here. Heck, I might buy it for the right price.
Jason
 
Don Nguyen said:
My mom's sewing machine has a foot pedal connected to some transmission gizmo on the motor and allows for speed control. No idea about torque/rpm stuff with that, but it's pretty neat.

I'll go look into it...
Click to expand...
It's almost surely a DC motor. Model trains, slot cars, and lots of other equipment run on DC for variable speed.....


Medicevans... If you buy the single phase motor, then you will need step pulley's like on a KMG. Go to Beaumonts site and price out the pulleys, pillow blocks etc, and you'll see you're not saving much vs getting a 3ph motor with a VFD.
Maybe look at the Vacon or TECO VFD drives to go with a 3Ph motor.... The "standard" is a KBAC27D, but some people use other VFD's with success....

Sam's illustration above helps....

This is what I did.... I bought a KBAC27D VFD, a 3ph 1.5hp motor for my GIB. The cost for the VFD was $400ish. But here's the pay off.
I just bought another 3ph motor off eBay for my disc grinder, now I have variable speed to two machines for the cost of a single VFD and some switches. I plan on adding one more disc down the road to run off the same VFD.

If you did by that motor, you can add a 6" drive wheel and use as is. But it'll be single speed.....

Also, I assume you are looking at 56C motor frames, with TENV or TEFC housing?
 
jawilder said:
I guess I am confused. Are you saying that you currently have access to 3 phase power in your shop? If that is the case then you can use single or three phase motor. If you have a good deal on a 2hp single phase motor then get it and use step pullies. No, you can't fine tune them like you can with a VFD, but they work well with step pullies. The $75 pullies may be the bees knees, but the $10 ones from Ace hardware work well too. I use them and haven't had any issues at all.

I was given a 2hp pool pump motor and use it with step pullies. I think I have about $70 in my step pully setup and love it. If the motor is cheap, go for it. If you don't like it you can always sell it on here. Heck, I might buy it for the right price.
Jason
Click to expand...

No, I have 20 amp 115VAC and 30 and 60 amp 240VAC. The reason I wanted to know if a single phase motor would run on three phase power was I have a source for a NEMA 12 3hp VFD for $200 that is 240V single phase in/3 phase out. However, there are three motors I'm looking at. There are a cheap 1800 rpm single phase 2 hp, cheap 3600 rpm 3 phase 1.5 hp, (both same supplier) and more expensive 3600 rpm 3 phase 2 hp.

I'd really like to use the single phase 2 hp because it's so much cheaper, but if it wont work, it won't work.
 
Won't work.

I found a 2hp 3ph 1800 rpm TEFC with foot for $180 free shipping.
Is that "cheap" or expensive to you?
 
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