Lathe vibrations

Hi all.

Just a quick up date.

Removed the motor wires from the invertor. Run a new feed wire from the inverter to a used ABB 1.1 kw 3 phase motor. The motor was sat unbolted on the cross slide and the inverter turned on. Motor ran quickly up to speed with negligable noise and vibration (only what i expect from an electric motor) whilst running no vibration evident in any part of the lathe. Removed the new wires from the ABB motor and connected them to the lathe motor. Turned on inverter. Lathe and motor body vibrated. For some reason the motor and inverter do not appear to be compatable. As the motor has misbehaved with two inverters, then it appears to be time to replace the motor

So, i propose to take off the original 3hp motor and replace it with the ABB 1.5 hp motor. Next question, do you think the lower powered motor will be man enough to run the Colchester Student. It is not used for production work just making parts for my motor bike etc. Or can anybody recommend a source for aquiring a suitable motor and the what size should i use?

Thanks for your help

Peter

A photo of the wiring inside the motor's connection box may assist someone to help you diagnose the issue with your motor.

Whereabouts are you in the country?

Bill

Have you investigated the connections from the stator to the terminal block? You relate a tale of a similar problem and the solution. The fact that the motor ran happily in the star configuration and has only been rough since the conversion to delta and driving from a VFD would tend to indicate that something has gone wrong at that point. One of the questions to ask when fault finding is 'what has changed? In this case a VFD and the star to delta change. If possible run the motor in star on a three phase supply and this should show if the motor has a fault like a broken rotor bar or loose rotor or a winding fault. If it runs smoothly then you need to revisit your delta connection. I have encountered quite a few motor faults in 44 years of industrial maintenance but although I always believed it to be important to have the windings the correct way round I had not encountered the problem except when winding motors as an apprentice I got a coil the wrong way round and the motor did not like it, very rough running. Murray raised my interest by declaring it did not matter which way the windings were connected, this was contrary to my belief so I had to test it, reversing one winding did indeed make the motor run rough and also change direction. The symptoms sounded very like your original post so my approach would be to prove that the wiring of the windings to the terminal block are correct. A squirrel cage three phase motor is an extremely robust device and faults are rare but of course anything is possible.

Mike

Mike's suggestion is good with the caveat that swapping a winding over in star has exactly the same effect!

A lot of the comments and suggestions have been made on this already but has the VFD got an Autotune function? I use makes like Parker SSD, ABB Drives, Telemecanique & Mitsubishi types on my machines. These are usually aquired off eBay. As paying full price it a bit costly to say the least! 😳

John

Hi all

For info the windings have letters and numbers on each. I have connected

B2 to C1,

A2 to B1 and

A1 to C2.

Each of the inverter utput wires connects to each of these pairs. Does this appear to be correct?

Thanks Peter.

That is what I would have done. The acid test is does it run smoothly? If not then it won't take long to swap each coil round one at a time and see if it makes a difference or you could run through the process linked to in a previous post. Most inverters will not need too many parameters to be set from the out of the box setup just to run the motor.

Mike

Edited By Mike Poole on 14/12/2017 21:04:46

Hi Mike.

Sorry to ask stupid questions, do you mean swoping the 3 inverter output wires around, as i initially did this to correct the rotation of the motor (swoped two of the three wires). I have wired the inverter input control into the lathe switch gear. As such the start, stop and forward/reverse switches on the lathe control the input switches on the inverter. The only external change to the lathe is the addition on a 10k pot.

Regards Peter

Peter, before I read your last post, I've tried to answer that one in a PM. The suggestion isn't to swap the supply wires round, rather swapping the orientation of one of the sets of windings which form one side of the triangle of windings in delta configuration.

Bill

I hope this copies OK and explains the thoughts of some on here.

Very well explained Bill, I think this has to be tried as it at least needs to be ruled out of the possibilities.

Mike

Hi All

Thanks to Mike and Peak4, very well explained.

I've just come out of the garage after working in the base of the lathe changing around the wiring as suggested.

On each of the winding wire changes the motor ran much slower, rougher and grumbled as if it had a knackered gearbox.

So I think the wiring was originally correct. As you can imaging after all i have done to this lathe, i think i would be better off sat in the pub with a glass of real ale!

I'll now have the day off it and i think change the motor which brings me back to, do you think 1 and a 1/2 hp motor is adequate for the lathe and if not what would you fit.

Thanks again for your help, and have a good weekend

Peter

Edited By Peter Smith 25 on 15/12/2017 10:57:40

To recap where we are upto:

The motor used to run ok on a previous converter setup.

The motor bearings have been replaced.

The rotor with pulley fitted is well balanced.

The motor windings are wired correctly and no winding is incorrectly labelled or reversed.

The motor produces a vibration with the belt removed.

The inverter can run a smaller motor smoothly but the same settings do not work on the original motor.

An alternative inverter produces the same symptoms.

----------------------------------------

Do you have the details from the motor plate? ( ideally a picture). Does the plate show the delta connection voltage to be around the 230v area and star 415v. What is the Full load current for each configuration and can the inverter supply that current?

Mike

Using the smaller motor of 1.5hp may well be ok, you may have to use some longer ramp times to get things moving but if the drive train doesn't need too much of the 1.5hp you may be ok as long as you don't work it too hard. I expect the frame size of the motor is smaller than the original so will need a packer to get the shaft height correct or a longer belt if there is not enough adjustment. The shaft diameter is probably smaller so a new pulley may be easier than a sleeve setup.

Mike

It would be helpful to see if the balance of the phases of the inverter goes off at the load of the 3hp motor comes on, one or two of the phases may not be up to the work.

Ian S C

Hi Mike and guys

Sorry i've tried to upload photos but failed miserable, so the motor plate info is

Type D90L

V220/250-380/440

A 8.7/5 3HP DE 125P

1410 RPM HZ 50 IC1258

Inverter info is not listed in the printed sheets but on the side of the inverter is a sticker with

Input:AC 1PH 200-240V 50/60HZ 20A

Output:AC 3PH 0-240V 0-200HZ 3HP.

Hope this helps

Regards

Peter

Before yo go spending more money I would look at the torque boost setting on your inverter - after all pressing a few buttons won't cost you anything, Set the torque boos (parameter F09 on the jaguar cub range of inverters) t to 'constant' (option 3 and I imagine the problem will vanish like the Scotch Mist. Stop buying unknown cr%*and buy from somebody trustworthy who can support you!

IKB

Hi Isimbard Brunel

Thanks for your input.

Would altering the torque setting (F13 on my inverter) effect the vibration which is evident at all motor speeds, with and without the drive belt fitted? The vibration is evident running the lathe, taking light cuts or even cuts of 100 thou per side (which it will do without much problem).

Thanks

Peter

Whilst appreciating the potential electrical hiccups is there any mileage in there being a problem with the bearings?

I know that you have checked the balance of the rotor and pulley but this was outside of the motor frame.

Are the bearings tight and square on the shaft?

Are they a good fit in the motor casing itself? Did the casing go back together in proper alignment?

Just clutching at straws here.

Hi all

As an experiment, i changed the inverter torque control settings to 3,7, and max 10. None of them made a scrap of difference, so that's it for this motor. Tomorrow i'll pull the lathe away from the wall, (no mean feat) and swope the motor for the 1.5 hp.

I'll let you know the outcome.

All the best

Peter