Converting older 3 ph motor to delta

[robgraham]

I've the task of running a Harrison wood turning lathe with a 3/4 hp

3ph motor on single phase.

I've an electronic box which converts 240v single phase to 240v 3 phase and I've had running a modern 3ph motor, but the motor from the Harrison lathe ( Griphon from Brook Motors) is an old one and is connected in star configuration for 415v operation.

Has anyone tackled taking an older motor such as this apart to get access to the coil ends and reconnect as a delta connected motor? I can't imagine that motors of this age - possibly 60 years old - are that much different in build but I don't have quite the confidence I had in my teenage years for taking things apart and getting them back together again successfully so I'm looking for some words of encouragement!!

Thanks Rob

[Andrew Mawson]

Rob,

Yes I've done it - it's fiddly and if the coils are shellac'd (which they probably are) it makes getting the thing apart 'interesting'. Make sure that you use wire and sleeving that will stand the temperature and both lace it and shellac it to ensure no fretting. The bigger the motor the easier it is. Smallest I've done was the suds pump on a Colchester Student lathe - 1/6 hp iirc - all a bit tight in there!

AWEM

[robgraham]

Hi Andrew Do I take it that you withdraw the rotor and work inside without removing the coils ? Shellac I have in the form of I use for French Polish - I take it that's the correct form? But what is suitable for the re-lacing ?

I was just thinking that gentle application of meths will ease off the existing shellac.

Many thanks - these are just the words I was looking for. Rob

[Andrew Mawson]

Hi Andrew Do I take it that you withdraw the rotor and work inside without removing the coils ? Shellac I have in the form of I use for French Polish - I take it that's the correct form? But what is suitable for the re-lacing ?

I was just thinking that gentle application of meths will ease off the existing shellac.

Many thanks - these are just the words I was looking for. Rob

Yes, rotor out and work on the coils. I wouldn't use meths - itmay go further than you want - just gentle teasing out with a scalpel blade. Use strong cotton for lacing, not plastic

AWEM

[robgraham]

ote:

Back again already, sorry ! I've released the through bolts and tapped out the end plate but ..... the bearing is holding it and the rotor in. Do I need to take off the pulley block and the plate at the front end -(I'll have to go and cadge a puller from the works up the road a bit) and then do I have to arrange some sort of pressing action in order to get the shaft clear of the rear bearing ?

Cheers and thanks

Rob

[geoff]

In message , Andrew Mawson writes

I've got a reel of lacing cord if someone wants a few metres

[Andrew Mawson]

motor?

confidence

(which

blade.

Back again already, sorry ! I've released the through bolts and tapped out the end plate but ..... the bearing is holding it and the rotor in. Do I need to take off the pulley block and the plate at the front end -(I'll have to go and cadge a puller from the works up the road a bit) and then do I have to arrange some sort of pressing action in order to get the shaft clear of the rear bearing ?

Cheers and thanks

Rob

You >may< be able to get at the star point without pulling the armature - do a bit of investigation before further dismantling

AWEM

[Fred]

Have you considered 3 x 240V isolating transformers, where the primaries are connected in star and the secondaries in delta? Given it's a 3/4 hp motor we're not talking large transformers?

Save dismantling the motor and disturbing the windings.

[robgraham]

ote:

I'm hoping so but I still have the problem of getting the plate off at the end which carries the terminal block. I can see the coil ends by taking the terminal block off - only see - but I can't progress without separating the shaft and the bearing so that I can get the end plate off.

Rob

[robgraham]

Geoff and Fred - thank for your offers and ideas. I'll see how I get on and perhaps act on them.

Rob

[terry]

Or you could perhaps use that stuff for cleaning your teeth; er, er. got it! "Floss'. But waxed lacing twine is easier to use.

[robgraham]

Just replying to my own post to say that I found that the end bearing is clamped into the end part of the body by inner and outer plates screwed together through the body end, and is not tight so the end part of the body came off with no bother after all that. I've now got access to the coils !!

I know this is not the sort of problem we all tackle but with the access to affordable 240v inverters, this modification is becoming more popular, so I'm taking some photos as I go along and will post the link to them in due course.

Rob