Motor vibrations problems

[savarin]

I am thinking of swapping out a single phase motor for a 1.5hp 3 phase motor controlled with a vfd.
Why? Because the brand new motor produces a lot of vibration on my drill press (and lathe) that I would like to remove.
I had the motor replaced under warranty but its still the same.
Its not in any of the pulleys as I removed everything off the motor and it still vibrates things off the table.
What I want to know is:-
Will a 3 phase motor run smoother?
Whats best 2, 4, or 6 pole motor?
Does the number of poles relate to total speed?
Does the number of poles have a bearing upon torque?
Probably more questions but I havnt thought of them yet.
Thanks

 

[mksj]

It will run smoother, but to some degree depends on the motor you purchase. There are many good motors that you can find at very reasonable prices, but you need to be sure that the frame size fits. Your current motors name plate would be helpful, I would replace it with a motor having the same number of poles/RPM. Motor torque goes up linear as the poles go up, but RPM goes down. Given the same spindle speed, torque will be the same for 2, 4, 6 pole motors due to different drive ratios.

There are limits to over speeding motors 4P is more ideal.

 

[jbobb1]

Curious as to how long the first motor was in service? Single phase motors do vibrate, but shaking things off of a table seems a little extreme.

 

[C-Bag]

Wonder if the culprit is the pulley being out of balance?

 

[savarin]

Not the pulleys, they are removed, the motor seems to have a harmonic vibration.
It didnt change with the replacement motor, only 1 day old, but from the way work appears to be done these days maybe they just sent back the original as it still looked brand new.
The lathe has this kind of vibration as well but not as bad, also from new in 2012.
Maybe its me being a damn picky a$$hole but its very annoying and I just wondered if the 3 phase change would be smoother.

 

[C-Bag]

Oops, didn't see you mentioned the pulley's being off. I know in all the discussions about surface grinders folks are warned not to replace the 3 phase motor with a single phase because of vibration. If nothing else a 3 phase with a VFD would help with speed control. I've been eyeing the move to a sewing machine motor because of speed control and low speed torque. Nobody has said anything about vibration.

 

[hman]

It's a pretty nasty situation when the motor itself has a wobbulation. Electric motors are supposed to be smooth running! Other than replacing it with a 3 phase or "professional level" DC sewing machine motor (per C-bag), I'd guess your only alternative would be building a balancing stand, disassembling the motor, and checking/correcting the balance of the armature. Just what you wanted, eh wot ... another project. Wish I could offer a magic bullet, but I'm fresh out.

PS - I've returned items for replacement on occasion. If I think of it ahead of time, I'll make a "secret" mark in an unobtrusive place and photograph it "for the record" before sending it back. Then check the "replacement" to be sure it's not the same one. Of course, if they've had to replace more than one motor for the same problem in the past, they may well have a "stock" of lemons, that they keep rotating between customers. Am I being paranoid? Ya, sure, you betcha (once in a while)!