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Three Phase AC Phase Conductor Colours - Mandatory?

Fraser Donachie

An LV Switchgear manufacturer has correctly used Brown, Black and Grey conductor colours in their panels. But the assignment is not the "preferred" L1=Brown, L2=Black & L3=Grey. Instead, the phase sequence is different. Whilst this is extremely undesirable from a safety and human factors viewpoint, is it 'illegal' or would it mean their DofC is invalid? IEC 60445 does not specify the assignment between L1, L2 & L3 and Brown, Black or Grey. I believe CENELEC HD 308 S2 may specify the "preferred" assignment but I cannot obtain a copy of that. How mandatory is the "preferred" and generally accepted assignment L1=Brown, L2=Black & L3=Grey? THANKS!

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  • 0

    However, not sure what all that has to do with the fact that you're seeing L1, L2 and L3 on equipment terminals, when the standards say they should be U, V and W?

    From purely a common sense point of view, it does seem sensible that the terminal labelling matches the requirements of BS 7671 table 51 for markings on the conductors themselves.

       - Andy.

  • 0 in reply to AJJewsbury
    AJJewsbury said:
    From purely a common sense point of view, it does seem sensible that the terminal labelling matches the requirements of BS 7671 table 51 for markings on the conductors themselves.

    But that can't be the case for all equipment, because the phase rotation may not be L1-L2-L3 ("clockwise") in the installation. And indeed BS 7671 doesn't require it to be either.

    In a new installation, granted you could ensure the phase rotation is "clockwise" (despite it not being a requirement) but when connecting a new machine to an existing installation where this isn't the case, you'd just have a mis-match of terminal identification vs conductor identification. I think this is why U, V and W are recommended for equipment.

  • 0 in reply to AJJewsbury

    I have had many experiences of connecting three phase motors contained in machines on many sites. We always had to safely test for correct rotation of motors after installation with gearboxes disconnected or set into neutral drive , or drive belts removed as the rotation was  a 50/50 chance  gamble of correct rotation. Whether the supply cables were numbered or identified by colour the motor direction still had to be tested very carefully. After a motor rewind a motor could rotate backwards compared to before it was sent away for the rewind.

    Z.

  • 0 in reply to Zoomup

    This is exactly right. Our facility used to have what we always called Sheffield rotation, which was corrected at the intake years ago, and then sub mains were changed to correct it. 

    Now, its anyone guess and like you said, you connect a motor, or machine and check the rotation every time. We would never rely on conductor colours, even just to assume black is phase in a new colours cable. 

    In a situation described by the OP, we would check and correct the phase order on the panel intake

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  • 0 in reply to Zoomup

    This is exactly right. Our facility used to have what we always called Sheffield rotation, which was corrected at the intake years ago, and then sub mains were changed to correct it. 

    Now, its anyone guess and like you said, you connect a motor, or machine and check the rotation every time. We would never rely on conductor colours, even just to assume black is phase in a new colours cable. 

    In a situation described by the OP, we would check and correct the phase order on the panel intake

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