Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 39 replies
  • Subscribers 40 subscribers
  • Views 7005 views
  • Users 0 members are here
Options
You may also be interested in
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

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!

  • 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

  • 0 in reply to gkenyon
    gkenyon said:
    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.

    So let me check that I understand this please. Selection of the first phase is arbitrary, but we call it L1. Then L2 could be 120º behind, or it could be 120º in front depending upon where you are. So the phases rotate L1, L2, L3 or L3, L2, L1.

    I am glad that phase rotation was checked when I had my supply put in. Nonetheless, I shall know to change the plug rather than the socket if my bandsaw goes widdershins.

  • 0 in reply to Chris Pearson
    Chris Pearson said:
    gkenyon said:
    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.

    So let me check that I understand this please. Selection of the first phase is arbitrary, but we call it L1. Then L2 could be 120º behind, or it could be 120º in front depending upon where you are. So the phases rotate L1, L2, L3 or L3, L2, L1.

    I am glad that phase rotation was checked when I had my supply put in. Nonetheless, I shall know to change the plug rather than the socket if my bandsaw goes widdershins.

    I don't quite understand what you are saying here.

    I have worked with installations that clearly have L1, L2 and L3 phases, that were, at the time, coloured Red, Blue, Yellow respectively ... but the phase rotation was definitely "L1, L3, L2" (or, if you prefer, L3, L2, L1 or even "L2, L1, L3") ... but it's not possible to ascertain which.

    BS 7671 doesn't require (and no other standard appears to require) phase rotation to be "clockwise" (and it can't because there are some areas, and installations, that are like that already). So, in the real world, yes you may have phase "rotation" that is anticlockwise, and you'd need to address that when connecting equipment?

  • 0

    So, in the real world, yes you may have phase "rotation" that is anticlockwise, and you'd need to address that when connecting equipment?

    Indeed - which is why there's a market for plugs that can easily swap L2 and L3 around - e.g. https://docs.rs-online.com/b3c1/A700000007615767.pdf

      - Andy.

  • 0 in reply to gkenyon
    gkenyon said:
    BS 7671 doesn't require (and no other standard appears to require) phase rotation to be "clockwise" (and it can't because there are some areas, and installations, that are like that already). So, in the real world, yes you may have phase "rotation" that is anticlockwise, and you'd need to address that when connecting equipment?


    Something else that I have learned from this wonderful forum!

    That all seems very bizarre. So numerical order counts for nothing and indeed the same for alphabetic (U, V, W).

    Back to the OP: it seems rather pointless to assign brown to L1, black to L2, etc. because the phase rotation could be brown, black, grey; or brown, grey, black.

    I suppose that what really matters is that the rotation is all the same within an installation; and as Zoomup points out, all motors should be checked for rotation on commissioning and after repairs.

  • 0 in reply to Chris Pearson
    Chris Pearson said:
    I suppose that what really matters is that the rotation is all the same within an installation; and as Zoomup points out, all motors should be checked for rotation on commissioning and after repairs.

    That's it ... the point is to identify L1 the same throughout the installation, L2 the same throughout the installation, and L3 the same throughout the installation.

    Whether the phase rotation is L1, L3, L2 (counter-clockwise) or L1, L2, L3 (clockwise) is quite arbitrary and irrelevant regarding identification.

Community Rules & Guidelines