3-phase: a thought-provoking recondite conundrum

hi all,

I finally got my 3 phase lathe working off a phase converter and as some of you warned me, the motor initially turned in the wrong direction. Now I know all I have to do to correct this is swap two phases, but the que stion I want answered now is, could I have avoided this extra task if I'd a ssumed from the outset that a swap would be needed and just done it before even switching the thing on for the first time?

cheers.

Reply to
orion.osiris
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IME, if you do that, it is the only occasion it would have gone in the right direction first time.

Colin Bignell

Reply to
Nightjar

e of you warned me, the motor initially turned in the wrong direction.

question I want answered now is, could I have avoided this extra task if I 'd assumed from the outset that a swap would be needed and just done it bef ore even switching the thing on for the first time?

Right, so the best advice is to swap the wires over immediately before test ing the motor for the first time; thanks.

Reply to
orion.osiris

It does make you wonder, how many 3ph supplies actually have the phases correctly identified... you would think that keeping L1 matching L1 and so on through the installation you should get something better than 50% right first time!

Reply to
John Rumm

If you are using a converter (as distinct from an inverter) It is worth making sure that the switchgear contactors are not supplied from the artificial phase but direct from the internal auto transformer. This is because the voltage on the artificial phase can be all over the place especially during motor starting and the last thing you want is the contactor dropping out when you start up.

DAMHIKT!

Reply to
Bob Minchin

Well, quite. The supply cable that came with this 3-phase welder I bought had all 3 phases colour coded the same shade of brown. Not sure what year that scheme became impermissible!

Reply to
orion.osiris

e of you warned me, the motor initially turned in the wrong direction.

question I want answered now is, could I have avoided this extra task if I 'd assumed from the outset that a swap would be needed and just done it bef ore even switching the thing on for the first time?

Not entirely sure what you're on about here, Bob, but I'm using a *static* converter: 230V single phase in; 230V three phase out.

Reply to
orion.osiris

Well as I supervised the installation of my 3 phase incomers, and wired all my (extensive) three phase installation myself I can with confidence select L1, L2 & L3 in any of my five buildings and KNOW that they are correct. I also use a phase rotation tester each and every time I install a three phase socket. (which seems to be a fairly frequent occurrence of late)

AWEM

Reply to
Andrew Mawson

Covered that several posts ago, but pearls before swine I think . . . . . . . .

AWEM

Reply to
Andrew Mawson

Not according the Murphy.

Reply to
dennis

A sign of a man with too many new toys ;-)

Reply to
John Rumm

I finally got my 3 phase lathe working off a phase converter and as some of you warned me, the motor initially turned in the wrong direction. Now I know all I have to do to correct this is swap two phases, but the question I want answered now is, could I have avoided this extra task if I'd assumed from the outset that a swap would be needed and just done it before even switching the thing on for the first time?

There is an expensive instrument that will indicate phase rotation. No-one buys them because it's easy to perform the experiment with a 50/50 chance of first time success. Few things are damaged by going backwards. As you clearly don't have any luck, do not buy any lottery tickets. :-)

Reply to
harryagain

Not entirely sure what you're on about here, Bob, but I'm using a *static* converter: 230V single phase in; 230V three phase out.

Most of them rectify the AC 1 phase and then generate the 3ph "from scratch"

Reply to
harryagain

Bollocks Harry - you are talking about an INVERTER not a converter. A world of difference

Reply to
Bob Minchin

Is such a thing possible?

Reply to
Grimly Curmudgeon

On reflection, probably not ;-))

Reply to
John Rumm

Well it's got to the stage where more and more is going back on ebay just to create a bit of elbow room .....

AWEM

Reply to
Andrew Mawson

If its going back at more than purchase price, then its not a bad thing...

Reply to
John Rumm

You could have avoided it by using an inverter and just changing the labels on the forward and reverse buttons.

Reply to
The Other Mike

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