Electric motor vibrations

[Sonic EscapeParticipant @sonicescape38234]

I just bought this electric motor but I noticed that it has some vibrations and I don’t know if it’s normal. It’s best noticed if I put it on a hard surface. If I hold it in my hand, the vibrations are very clearly felt. I removed the reducer and nothing changes. Would that be a valid reason to return it? Or this is expected for this low price?

 

[EmgeeParticipant @emgee]

You could try splitting the motor from the gearbox to check the motor for vibration, in case it is from the gear train.

 

Emgee

[Sonic EscapeParticipant @sonicescape38234]

Is the same without gearbox. Actually they are shipped separately. I started the motor alone first and it is vibrating exactly the same.

[John HaineParticipant @johnhaine32865]

Awful!  Even a commutator motor shouldn’t be that bad.  Send it back.

[noel shelleyParticipant @noelshelley55608]

doesn’t sound good ! Cheap bearings or a poorly balanced rotor ? A single phase motor will sound bad laid loose on a sounding board. Consider sending it back or look at the bearings and may be replace with good ones. Noel.

[duncan webster 1Participant @duncanwebster1]

If you replace the bearings and it doesn’t improve then at least under uk law you won’t be able to send it back

[John HaineParticipant @johnhaine32865]

If it was bought new then SEND IT BACK. We are too ready to try to fix things when the supplier is responsible.

[Sonic EscapeParticipant @sonicescape38234]

I’m want to send it back. But I’m afraid this is now just a bad motor. But they all are like that. I don’t want to send me a new one.

Is there a significand noise difference between a single phase and a similar three phase motor? Of course assuming the bearings are ok, the rotor is balanced and so on. Because I have a spare inverter that I could use. Back home I have some 3 phase motors and I remember they were very quiet. Unfortunately they are to big and heavy to ship them where I live now.

[John HaineParticipant @johnhaine32865]

Money back job then.  Single phase tend to be noisier and vibrate more, 3 phase generally are very smooth.  But single phase shouldn’t be as bad as that example!

[PeteParticipant @pete41194]

Fwiw and it may or may not apply to your motor, I suspect it probably does though. According to the industrial electrical dealer I talked to, and in general, there’s two electrical motor standards in use in most places in the world for the output shaft size, any key way dimensions, face or foot mounting frame standards, PCD dimensions for the mounting bolts in those face mounted motors etc. Those would fall under the electrical motor standards for either metric or imperial dimensioned motors.

However, there’s also a third and for whatever reason less well known Asian set of those electrical motor standards that don’t quite match either of the other two. Any off the shelf metric or imperial standard electrical motor, and especially for those face mounted motors may be unlikely to be interchangeable with what you already have. For that exact reason my own Taiwanese manufactured mill has a 2 hp 3 ph face mounted motor that can’t be matched with anything off the shelf unless I were to machine the correct adapter plate first. Even then, the shaft diameter and key way would likely require further machined parts. Or I replace it with a motor built to those same Asian dimensions. Luckily my mill came with one of the smoothest operating motors I’ve ever used.

As you’ve already thought, any replacement motor from the same source may be just as bad for all of them or you’ve just gotten a bad one. But for any use I’d want a 90 degree gear reducer like you have, I’d certainly want far better than that. Anyone who thinks any mechanical item is always much cheaper from the far east and has that much lower price only due to the lower labor costs really hasn’t thought it through very well. A vastly lower price for any comparable product is an guaranteed indicator that steps were missed, ignored or corners cut right from the material quality, any heat treatment, grinding, motor balancing etc.

With today’s high volume production, automation methods are also pretty much standard even in most Asian counties. For the same degree of accuracy, quality and durability, the out the door costs for any manufacturer are going to be very close to the same today no matter where it’s being produced simply because the cost of that labor has so little effect on it’s final price. As just one simple example, I’ve operated mining equipment where the fuel and maintenance costs were well over 30 times what I was being paid per hr. Depending on it’s commercial or hobbyist’s end use, any products quality and durability may or may not be the most important item. Although buying simply due to the lowest possible price has never worked out very well for myself. I highly doubt that’s going to convince anyone here because that seems to be something all of us have to finally learn the hard way.

[Sonic Escape]

On Sonic Escape Said:

I’m want to send it back. But I’m afraid this is now just a bad motor. But they all are like that. I don’t want to send me a new one.

Is there a significand noise difference between a single phase and a similar three phase motor? Of course assuming the bearings are ok, the rotor is balanced and so on. Because I have a spare inverter that I could use. Back home I have some 3 phase motors and I remember they were very quiet. Unfortunately they are to big and heavy to ship them where I live now.

A properly constructed single-phase motor should run smoothly and without excessive noise and vibration – some old Brooks are virtually silent..

In the UK there are distributors for equipment such as TEC who must have some control over QA and supply a useable product at a mid-range price – there must be similar in EU?

These days I think maybe an old but used ‘branded’ motor can be a better buy than the cheapest Far-eastern.

 

 

[JasonBModerator @jasonb]

Take the fan shroud off the end of the motor and make sure the fan is not hitting the shroud or motor body. I had that once where it probably got dislodged in transit. Quick and easy to fix.

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