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Annoying electrical problem

I got my 'new' CVA lathe in its intended spot last night, with this evening allocated to get the electrics sorted. These things weigh 1.5 tons & the electrics are all behind a door at the back, so I want it right before it's hidden by the other lathe which will be backed up to it. My heart sank when I read the label on the panel "control voltage

240V" . That means the contactor coils are 240V, so it needs a neutral, but my 3-phase comes from a converter with no neutral, & the wiring is all 3 phases plus Earth, to 4-pin sockets :-( I've either got to change the contactors (3 of them!) or find new coils for them (unlikely) or rig up a 240V supply. I reckon my best bet is to fit a small transformer to the board to give me 240V from two of the phases, it only needs to be a few VA to run the coils, but where to find one? Ideally with a few tappings to get the voltage right, as some contactors are fairly fussy about voltage. The whole job of shunting the workshop around has to wait now until I can sort it. I know I could run another cable in from a 240V socket, but it's messy and there isn't a socket near the machine Andrew, have you got anything in your clearance mountain? How have other people got round this problem, I know it's not all that unusual to have 240V controls on 3-phase stuff?

Cheers Tim

Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

Reply to
Tim Leech
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Tim,

Yes I have a solution for you - a smallish 415 to 240 v transformer

Apply to the Mawson Shop for details !!!

AWEM

Reply to
Andrew Mawson

Here's one in Farnell:

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it's a common requirement and you will find others in there if you search for "transformer" and use the parametrics.

Greg

Reply to
Greg

Thanks to both, hopefully Andrew has something which will do the job.

Cheers Tim

Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

Reply to
Tim Leech

Got any spare lo-volt lighting units round? These usually have dual wound 440240 inputs and 12/24 outputs. Feed 440 into the box at 0 and 440 and take 240 out at 0 and 240.

Failing that I have some here if you want to collect with your mic and welding gear as nauseam...........

-- Regards,

John Stevenson Nottingham, England.

Visit the new Model Engineering adverts page at:-

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Reply to
John Stevenson

I'd actually thought of that one, opened one up hopefully but it has

440V only input & a split secondary for 12/24. I remember now that when I converted my old Harrison L5 to single phase I had to use a 12V bulb on the 24V secondary as that was 440 in only. Now you've mentioned it I'll check in case the other one I have is different.

I've got to go to Newark & Burton next week or the week after, I'll hopefully collect them then.

Thanks

Tim

Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

Reply to
Tim Leech

Tim,

Picture on email to you with details - if you get back to me in time I'll pop it in the post this pm

Andrew

Reply to
Andrew Mawson

Thought I would check the lo-volt unit on the actual lathe, the lamp was missing & the previous owner had a mains Anglepoise reading lamp clamped on to a bracket. I found out why the lamp wasn't connected to it. Someone must have fitted a new transformer unit at some time, the wiring from the lathe control cabinet (440V) went into the *secondary* (25V) of the transformer, with the lamp connected to the primary!! The transformer itself might have survived, resistance readings with a DMM made sense though I haven't tried any AC or a Megger on it yet. Not surprisingly, the fuses had gone ;-)

It's no help for the other job, single 380/415/440 primary & 25V secondary.

Cheers Tim

Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

Reply to
Tim Leech

Feed it 12v and get 240 out

-- Regards,

John Stevenson Nottingham, England.

Visit the new Model Engineering adverts page at:-

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Reply to
John Stevenson

With my converter the 240 V runs a transformer, but one side ( the supply neutral ) is used as a leg of the three phase.

I have run a 240 V live wire to what should be the neutral pin on my three phase plugs, and take care to see all 240 V controls are run from the " neutral " three phase leg to the live 240 V.

With luck you may find the output of yours uses the 240 V live for one leg, and you can use the 240 V neutral on the neutral pin.

Hope this helps.

Regards Jonathan

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Reply to
Jonathan Barnes

Andrew

Received today, looks just the job, excellent service

I had hoped to get it fitted tonight, but after a long day welding in awkward positions (that's me in the awkward positions, the welding was pretty straightforward but I'm not as young as I was) it's going to be a large bottle of beer with the curry tonight & no work afterwards!

Thanks again

Tim Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

Reply to
Tim Leech

Thanks Jonathan

I had considered delving into that sort of thing, without going into the details, but decided that with my particular situation it will be easier/neater/possibly safer to produce the 240V within the machine.

If I were starting again from scratch wiring the workshop with 'synthetic' 3-phase I would certainly investigate the practicality of including a neutral.

Cheers Tim

Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

Reply to
Tim Leech

All part of the house clearance ! I have a further 3 or 4 of them !!!!!

Andrew

Reply to
Andrew Mawson

Idle bugger. You can't get the staff nowdays

-- Regards,

John Stevenson Nottingham, England.

Visit the new Model Engineering adverts page at:-

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Reply to
John Stevenson

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