# Three phase ac motors 110v help

1. Apr 30, 2009

### motorhed

I have a motor i am trying to get to work. The tag on it says its a three phase asynchronous motor. 110v and i think the current is 6.9amps. When i turn it on it hums and if i spin the motor it will start to go and will spin very slowly but as soon as any resistance is applied it stops and just hums. Now i did some research online and from what i understand 3 phase has 3 hot legs and is generally used in industrial settings. I have this plugged into my regular wall outlet which to my understanding is 110v single phase a/c.

2. Apr 30, 2009

### TVP45

Unless this is a very valuable motor, sell it for scrap and buy a single phase motor. I'm guessing you're in the US; you have single phase (2 phase if you want to split hairs) and it's expensive to change.

3. Apr 30, 2009

### RonL

Why do you want to get it to run?
If it is for a specific application, then as suggested a single phase motor will cost between $50-100 US, and is the best thing to do. If you are using it as a learning tool....? An electrical shop might check it for free, or a small fee, if it is good then look at the following link. A converter for that size motor looks to be around$100.00 US, and will change single phase to three phase.

http://www.phase-a-matic.com/PDF/SPL-2009-C.pdf [Broken]

Last edited by a moderator: May 4, 2017
4. Apr 30, 2009

### motorhed

It is actually for a machine. It just has a belt attached to it to spin. I have no problem buying a new motor but i want to pick one up preferably today or have one overnighted to me if anyone knows where i can get a similar one. Here is some more info on it, i need the new motor to be the same size as this one or similar because it is mounted to a bracket on the machine.

3 phase asynchronous motor
6.9A current
110v
1390 rev/min

That came straight off the tag.

5. Apr 30, 2009

### Bob S

I presume this is a 50Hz application. Is this correct? Is this a 1/2 HP motor? What is the rated temperature rise? What about shaft size, dimensional requirements, etc? Look in the Grainger catalog at
http://www.grainger.com/Grainger/wwg/productIndex.shtml?operator=retrieveProdLevel1Index&prodLevelList=Motor%257CMotors%252C&prod_level_selected=Motor [Broken]
or at

Last edited by a moderator: May 4, 2017
6. Apr 30, 2009

### motorhed

I believe the motor on there now is 50hz. Not sure what the difference in application is. I just did some research and a similar motor i would need would need these specs.

3/4 HP, 1/60/110 volt drive, 1,400 rpm.

Would one with more HP be better?

7. Apr 30, 2009

### motorhed

8. Apr 30, 2009

### Averagesupernova

Actually, I DO prefer to split hairs, and it is NOT 2 phase. Feel free to PM me or start another thread if you want to discuss it farther.

9. Apr 30, 2009

### TurtleMeister

I'm assuming the picture is of the 3phase motor you want to replace. Keep in mind that a single phase motor of comparable size may not have the starting torque required to run whatever it is you're putting it on.

10. Apr 30, 2009

### motorhed

starting torque is not a problem, i can manually get the machine going before i turn the motor on.

11. Apr 30, 2009

### TurtleMeister

Wouldn't hurt. It seems your main concern is mounting, shaft fit, RPM, and direction of rotation.

12. Apr 30, 2009

### TVP45

Lighten up. I put that in only because about third time I post on phase, somebody starts an ongoing argument. I'm too old to argue about this.

13. Apr 30, 2009

### motorhed

well i brought it to a motor shop and he said easiest way was to get this box that converts 220v single phase to 3 phase, works like a charm now. cost me like 150bux tho.

14. Apr 30, 2009

### Averagesupernova

Then you shouldn't have brought it up. You are now forever excused from arguing about single vs. 2 phase. However, if anyone else has questions, I'd be glad to answer.

15. Apr 30, 2009

### Staff: Mentor

Are you sure you didn't get ripped off? Why couldn't he have sold you a single phase motor in the first place?

16. May 1, 2009

### motorhed

He said a single phase was gonna cost alot more then the converter and would be alot bigger and id have to make a whole new bracket to mount it. Problem solved so im not rly worried about it, he was a nice guy and even let me go pick the part up without paying him until the next day and offered to help me wire the thing up if i needed help.

17. May 2, 2009

### TVP45

Since you won't let it be, I'll take part in a discussion if you want. My only interest is historical, but I'd still like to see some good opinions on this since it's one of the perennial questions (What's the difference between bolts and screws? What's the difference between pipe and tube? Should single phase be called 2 phase?). So, if you want, go ahead and frame a question. I'll put in my two cents.

18. May 2, 2009

### Staff: Mentor

There really isn't anything to that discussion. Here's a wiki on "two phase power": http://en.wikipedia.org/wiki/Two_phase

240V power is sorta in two phases, though, but it generally isn't called "two phase power" because it is actually just one phase of a 3 phase system that is then split in half. Ie, split phase: http://en.wikipedia.org/wiki/Split_phase
No need for a heated debate.

19. May 3, 2009

### TVP45

See? You could join in also. It's an endless discussion: Should we call it 120V 1Ph, 120V/120V 1Ph, 240V CT 1Ph, 120V 2 Ph, and so on? And, after that there's always the old one about "twist drills" vs "drill bits". Only engineers can truly love these arguments. If we beat this to death, there's always the age-old tangent of "If Herman Westinghouse had been Edison's brother, would we be having this discussion?".

20. May 3, 2009

### Averagesupernova

It's only endless when someone will not admit defeat. The wiki article should make you realize why calling 3-wire single phase '2-phase' is incorrect.