Lathe vibrations

[Phil WhitleyParticipant @philwhitley94135]

Hi Duncan, good post, to reverse a three phase motor you swap over any two legs of the incoming supply. You can do this at the motor, or the starter or isolator, or even at the plug if the equipment is plugged in. One of the first jobs we did at a completed installation was to phase out all the machinery and the socket outlets to make sure that all the equipment ran in the right direction, and that any machine, plugged into any socket, would run correctly. Many's the time we got despatched to a farm because the farmer had bought a new grain auger, and the first time he came to use it, it went the wrong way. They soon learned to do ot themselves!

[Peter Smith 25Participant @petersmith25]

Hi Phil.

I live just around the corner from the Dales Factory. The remnents of the workforce move out before the end of this year and it is planned to demolish it and build houses on it.

I've fitted the motor but due to xmas duties, the jobs come to a halt.

I will update everybody when it's back up and running.

Merry Christmas to all, and all the best for 2018.

Best wishes

Peter

[john fletcher 1Participant @johnfletcher1]

Hello Duncan I like your description. It is good practise to exchange any two incoming lines when reversing a three phase motor, and you will be successful every time. Exchanging connections on the motor terminal box you might be lucky on direct on line, but what about star/delta. I once went to a job where the customer has requested to have a motor direction of rotation reversed on a star delta starter/ motor, some one has rearranged the connection in the motor terminal box. The motor started OK on star but what a commotion on delta, it attempted to reverse. It took some time to work out what had happened and to reconnect the incoming lines in the correct manner. Stick with the lines and you always be successful. After a rewind we had a home made rotor mounted in a Perspex tube, the motor was connect up on a low voltage supply and you put the rotor inside the stator and noted which way it rotated, we also had a home made growler for locating stator winding faults. They wouldn't be permitted, now to dangerous. John

[Phil WhitleyParticipant @philwhitley94135]

Peter Smith , Gristhorpe? I used to race cars there in the olden days, and my late father new Lenoard H Dale personally, as he worked for the YEB. Seasons greetings to all, Bah Humbug, drink port and forget

Phil!

[Peter Smith 25Participant @petersmith25]

Hi all

Happy new year

As promised an update on progress with the lathe vibration problem.

Removed the 3hp motor and fitted an abb 1.1 kw 240 volt 3 phase motor.

The vibration felt in the lathe is much reduced and easily liveable with, however when using a tipped tool, taking a decent cut in top gear with the inverter showing 80hz, the lathe slows, so 1.5 hp is not enough to cope with tipped tools.

So, as i'm reluctant to use old second hand motors with the inverter, i've been looking at 2.2kw (3hp) 240v foot mounted 3 phase motors. I understand some cheaper motors are poorer qualty than others. Given the time and effort put into this lathe I'm considering a crompton greeves motor but there coming out at £200 plus vat and carrage.

Can anybody give me advice on how good these motors are or recommend a better ( and preferably cheaper) product

Thanks Peter

[peak4Participant @peak4]

Peter, you could see if one of the better known re-winders have any refurbished motors up for grabs.

e.g. Browill Rewinds near me; there's lots of others depending on where you live.

Bill

[duncan webster 1Participant @duncanwebster1]

Never dealt with them but this lot are from near where I was drug up, west riding of Yorkshire

**LINK**

keep an eye on

**LINK**

[Peter Smith 25Participant @petersmith25]

Thanks for your thoughts

I'm also from your area, i was brought up in Bradford, lived in Clayton, and Bingley, before moving to Scarborough in 1996.

Not much in the of industry over here.

All the best

Peter

[peak4Participant @peak4]

Just to update an old thread in case anyone re-visits it for reference purposes.

I've just picked up a nice little 3 phase 300w motor off a friend of mine, along with an inverter. I also had several spare inverters in stock, so I thought it a good time to re-form the capacitors in them and get everything tested ready for when I come to progress the next project. See this thread

The first inverter off the variac was a little Fuji, which I connected up to the motor; it ran as rough as a bears backside. The motor looked like it had previously been run off an inverter, as it was already set up for 240v.

Each phase out of the inverter measured the same voltage under load, with a multi meter, and gave a similar trace on my old single channel valve oscilloscope. (my 2 channel ex-GPO one has just expired. )

I then followed all the advice in this thread, including my own, involving coil polarities, swapping phases round etc.

Still just as rough, though some combinations of phase order were slightly smoother, but the motor was getting inordinately warm.

Next job was to try a spare brand new motor that I've bought for the DW mill, which ran just as badly.

By now, the second identical inverter was ready to take off the variac; this worked perfectly with both motors, as did the following two inverters.

 

Further investigation required to compare the two Fujis, which measured the same under motor load, both on the scope and a meter.

I then tried with the motor disconnected completely, and found the "U" phase reading about 70v low, and the scope trace for that phase, off load but with the inverter set to run, was also different.

Seems I have a duff inverter, but one which seemed to measure OK when under load, presumably due to back EMF from the motor windings misleading me.

I did mention earlier that I wasn't a sparky didn't I ?

 

Bill

 

Edited By peak4 on 01/04/2018 10:33:10

Edited By peak4 on 01/04/2018 10:34:41

[Ian S CParticipant @iansc]

Sounds as though you have a dud capacitor in one phase of the first inverter, things a bit out of balance.

Ian S C

[peak4Participant @peak4]

Posted by Ian S C on 01/04/2018 12:34:15:

Sounds as though you have a dud capacitor in one phase of the first inverter, things a bit out of balance.

Ian S C

That was my thought, but still to investigate; the maintenance schedule actually says you should replace the capacitors every 7 years.

Bill

[Peter Smith 25Participant @petersmith25]

Hi All

I purchased a brand new Crompton Greeves 3 HP 3 phase motor and fitted it to the lathe. The difference was amazing. Very little vibration, and surprisingly, the lathe gearbox in each of it's gears is much quieter. I've left it a while before responding to make sure the problem has gone. So clearly the old motor did not like 3 phase inverters. Thanks all for your help and thoughts, nothing externally to see as to what appeared to be wrong, but obviously electrical black magic at work. Keep up the good work helping each other. Regards Peter

[Neil WyattModerator @neilwyatt]

Posted by peak4 on 01/04/2018 10:32:12:

I did mention earlier that I wasn't a sparky didn't I ?

That's probably why you were able to spot it at all!

Neil

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