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3 Phase Motor Starters

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RussellT:
Thanks for the replies so far.  I'm sorry about the picture.  I couldn't open it either. :doh:  I just downloaded it to give you an idea what it looked like.  I've done it properly this time and reuploaded it above and now I can add a link to it in this post, so here it is again.



Is that anything like the one you have Andrew?

Thanks Bill I feel a little bit more comfortable about PCBs - though I understand transformer oil is often contaminated - but it's probably never been topped up. The motor is certainly more than a couple of horsepower - I can't see a rating plate as it's completely enclosed within the cast iron base of the lathe.  I think I need a mirror on a stick.

John, I wasn't going to rely on the conduit as an earth - I was amazed that there didn't appear to be anything else.  In fact I'm thinking about adding another earth wire back to the supply company's earth.  The fixed wiring has been done with 4 core SWA cable but uses one core as the earth.  If I used that core for a neutral I could also get the machine light working.  I could rely on the armour for the earth but I'd be happier with an additional earth wire.

Stuart - I'll talk to an electrician friend about earth and earth leakage testing.  I'm also considering adding an RCD. :zap:

I'd still welcome any other comments now you can see the picture.

Russell

lordedmond:
By ek Russell
That starter is a blast from the past I serviced those during my apprentiship I now 67 so you do the maths

They are oil filled as the contacts work in the oil bath , which is transformer oil vegetable based and stinks to high heaven

As the motor is a star delta wound one I would dump that starter and fit a VFD ,not to get the over speed but give a soft start , and no I did not miss the three phase supply that is installed ,but you can get three phase in and out units , failing that get a modern star delta starter with correct over load coils , best talk to your sparks as it's difficult to advise without hand on.

I did my time in heavy power with turbines up to six mega watt and motors to 3000 hp at 11kv

Have fun and make sure the machine is correctly earthed as per current regs
Stuart

dawesy:
Any pics of the lathe itself?
I have a churchill redman but mines a 7-cm
Be interesting to see if it's similar to mine. Mine has a 12-15" swing I'd estimate ( never actually measured it.

hermetic:
I also have some experience with Ellisons, albeit a bit bigger ones than that one, can you post up a picture of the motor, both ends especially, and a close up of the top of the starter to see what is on the top, there is usually a brass plate with the type and details attached to the oil tank, usually at the front. I wouldnt be at all suprised if this was a resistance starter for a slip ring motor, and unless this is a huge lathe, which I dont think it is, you may be better off changing the motor for something else more economical to run, as it wont be that efficient. I have just read the OP again, and I gather this motor is inside the machine. Has this starter ever been used to start this lathe, because if it hasn't the chances of starter and motor being compatible are fairly slim. If the motor is a plain three phase connected in star, and the starter is a direct on line one, then it should work, provided both starter and motor are in good condition, but I wouldnt put power on to the starter till you have dropped the tank on the starter and checked for any water or debris in the bottom, and I wouldnt put power onto the motor untill it has been megger tested, and the whole machine has been connected to a known good earth!! If the motor tests "low" it is not the end of the world, could be just damp, you can connect the windings in series and put a voltage onto it to dry them out.
Phil
UK

RussellT:
Thanks Stuart and Phil.

The starter has been on the lathe since the beginning of time so I'm sure they must be compatible.  I've been thinking about it and I'm fairly sure it can't be a star delta starter as I think there are only three wires out to the motor.  (There were three out to something else which isn't there, possibly a coolant pump - terminating in a box).  I think the lathe is fitted with a clutch - possibly to ease the start up load.

I shall be paying close attention to earthing and checking before I turn it on - and even then I might get its owner to turn it on. :zap:

Lee, I'll try and take some pictures next time I'm there.  It's a big lathe for a home workshop - the taper turning attachment looks like it would make a reasonable bed for a small lathe.

Thanks for the reassurance about PCBs - you've convinced me that they're the least of my worries. :med:

Russell

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