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Phase rotationL1 to L3, or L3 to L1?

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The question at the end: L1 to L3, or L3 to L1? The answer is in the notes below.

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Guidance Note 3 · 2.6.17 · p.93 for the phase sequence test — highlight it — and 4.8 · p.140 for phase rotation instruments. It is a live test, because it needs a live three-phase board.

What it is, in one line: a polarity check for a three-phase supply. It proves the phases arrive in the right order.

DisplayMeaning
Arrow to the rightCorrect — phases in sequence
Arrow to the left, or L lights upReverse — something is in the wrong place

The test sequence — and it has to be this way round

L1 to L2    then    L2 to L3    then    L3 to L1

That last one is L3 to L1, not L1 to L3.
Your hands cross over to do it. You are drawing a clockwise circle.
✋Get the last pair backwards and you fail a good board. If you take L1 to L3 instead of L3 to L1 you will get a left-hand indication on an installation that is perfectly correct. The right probe goes on L3.
Check the colours first. Brown is L1, black is L2, grey is L3. If a conductor is in the wrong terminal you can usually spot it by eye at the board before you test anything.
What reverse rotation actually does. A three-phase motor runs backwards. A domestic analogy: a drum turning the wrong way. Whatever the motor drives runs the wrong way too.
Not every instrument does it. A good approved voltage indicator will, some multifunction testers will, and dedicated instruments exist. Check before you need it.

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