3-phase: a thought-provoking recondite conundrum

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

Colin Bignell

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.

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!

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!

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!

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.

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

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

AWEM

Not according the Murphy.

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

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. :-)

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"

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

Is such a thing possible?

On reflection, probably not ;-))

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

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

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