Author Topic: single phase vibrations  (Read 194 times)

savarin

single phase vibrations
« on: May 12, 2020, 08:12:42 PM »
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.
It seems to be a high frequency vibration.
 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

jpigg55

Re: single phase vibrations
« Reply #1 on: May 12, 2020, 10:13:18 PM »
Doubling the poles halves the speed/RPM for a given frequency. This site explains it pretty well.
https://www.engineeringtoolbox.com/synchronous-motor-frequency-speed-d_649.html

I'm not completely positive, but I don't think 3 phase will have any difference.
Could the motor mounts be the cause of your vibration problem ?
I had a similar vibration issue on my mill that got worse the higher my spindle speed was. Terry told me to replace my motor mounts which got rid of the vibration.
SB 9A, Clausing 8520, Sanford MG 612

Terrywerm

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Re: single phase vibrations
« Reply #2 on: May 12, 2020, 10:53:19 PM »

Could the motor mounts be the cause of your vibration problem ?
I had a similar vibration issue on my mill that got worse the higher my spindle speed was. Terry told me to replace my motor mounts which got rid of the vibration.



Holy crap!  One of my suggestions actually WORKED!?!?!?


Boy, that'll teach me to open my big mouth!    :57:




Terry

Making chips with old machines!

savarin

Re: single phase vibrations
« Reply #3 on: May 12, 2020, 11:08:20 PM »
something I never thought of.
The motors on the drill press and the lathe bolt directly to the mounting plates thus transferring any high frequency vibration throughout the machine.
Maybe some isolating mounts in a softish rubber like these will solve the problem.
Worth a try and cheaper.


34_40

Re: single phase vibrations
« Reply #4 on: May 13, 2020, 04:49:58 AM »
I believe it was Billy G that did a thread about motor isolators on his mill on that "other" site.  I think he actually made the parts too???
Maybe he'll see this and reshare?
Clausing 108, Clausing 8520, Atlas Horizontal, Lincoln stick and mig welders

RayH

Re: single phase vibrations
« Reply #5 on: May 13, 2020, 12:33:55 PM »
As I understand your description of the symptoms (motor running, without a pulley, vibrates), I suspect that the rotating mass (the armature) is bent and/or unbalanced. In other words, a vibration induced by the AC frequency would be very low on my list of priorities.

Can you construct some sort of balancing stand (images linked) and check the armature? check the armature with the key and pulley mounted.

https://www.google.com/search?source=univ&tbm=isch&q=balancing+stand+images&sa=X&ved=2ahUKEwjF5_bMq7HpAhVmIDQIHbqtA_cQsAR6BAgIEAE&biw=1536&bih=722

The stand need not be fancy (for one time use).

Also, very bad bearings (assumed to be ball bearings) could be causing or exacerbating the vibration. Do the bearings feel good?

savarin

Re: single phase vibrations
« Reply #6 on: May 13, 2020, 10:10:25 PM »
This motor has been like this since new so a bent armature is I dont believe on the cards but,
being a reasonably cheap machine I can see the armature being out of good balance so that may be an avenue worth looking at.
I just went back and checked Bills solution and found I was asking about this in 2018 but never did anything about it.  :banghead:
I guess nows the time.
I need to find a source of the hard rubber.

woodchucker

Re: single phase vibrations
« Reply #7 on: May 13, 2020, 10:26:16 PM »
I was given a grinder and the thing bounced all over the place. The shaft was bent. Clearly it was like that new.
Not impossible. it depends how they make and build them.
Jeff
Clausing 8520   SB Model 9a - power hacksaw, Milwaukee band saw in a table.  Delta Rockwell Surface Grinder (not online yet .. being rebuilt where am I going to stick this)
For pics: https://imgur.com/user/woodchucker/posts

jpigg55

Re: single phase vibrations
« Reply #8 on: May 14, 2020, 08:01:03 AM »
SB 9A, Clausing 8520, Sanford MG 612