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Thread: Unbalanced jumpers

  1. #11
    Diamond Member Justloadit's Avatar
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    Quote Originally Posted by GCE View Post
    Aluminum gland plate is fine as it is non magnetic material and you will not get a heat build up due to eddie currents
    Only happens on magnetic material
    The one property of Aluminium, is that it generates eddie currents with changes in magnetic field, over and above the ability to absorb heat, and the reason that it is used in heatsink material in the electronics industry. Granted the strength of the magnetic field will influence the amount of heat generated by eddie currents. This property is not seen with steel, stainless steel and copper. In fact the steel is a good shielding material for radio waves and magnetic fields, as opposed to aluminium. However in this case that a 4 or 5 core goes through the plate, the sum of all currents in the phases will be zero, and no magnetic field will be created, however with single cable through the gland and the high currents you refer to, it will generate eddie currents. The amount of heat generated may be small enough that it may be ignored as normal operating temperature.
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  2. #12
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    Guy's we have managed to get an outage last night and I don't know how to attach the pics from my phone gallery and chat some more.
    Can someone assist me with doing this attachment.
    Thanks
    FRENCHIE

  3. #13
    Diamond Member AndyD's Avatar
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    Hi Frenchie, are you using a smartphone or a PC?

    On the very odd occasions that we enter cable conductors through separate holes via a gland plate we usually drill the gland holes in a straight line and then cut a thin slot between them before fitting the glands; this prevents heating occuring from eddie currents. If the current involved is less than 60 Amps we don't generally worry about it to be honest, I've only ever encountered heating problems due to eddie currents with supplies in excess of 200Amps.
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  4. #14
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    Hi Andi.
    I am working on my smart phone.
    I thought that aluminium not being magnetic it would not carry the field around the conductors, the conductors are +- 50mm apart, but you saying to cut the a thin line between the gland holes sounds the right thing to do.
    As mentioned previously we did the repairs, but because we were unable to see behind the switch gear, even trying to take pictures that didn't show anything wrong, we took heat scan and it only showed one of the parallel jumpers taking all the current and it was up 110 degrees, and the other had no heat at all.
    As all the guys on the chat including ourselves one thing came to mind is that their is a loose connection, but because of all the checking we did, we put that on the back burner.
    Well guys I am happy to say that I/we are very LUCKY still to be here chatting to you guy's ( once I manage to send the pics).
    A VALUABLE LESSON TO BE LEARNED.
    When we started to investigate this issue, i had my hands & arms and face hard up and behind the switch gear trying to ascertain the cause.
    When we replaced the two affected jumpers,
    The one overheated.
    The other not carrying the load.
    We found that the one lug actually slipped off the jumper and slipped back in like slipping on a glove, although it was crimped not correctly ofcourse, that particular lug was not the same as the other lugs on all the other jumpers.
    Could that have been one of issue that started the chain of events.
    I would like to give a special thanks to all of you guy's that participated in this discussion, and it did increase my knowledge in this debate.

    I will send the pics once I get the know.

    Thanks again
    FRENCHIE.

  5. #15
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    Greetings All

    I have to rectify a generator installation as the previous contractors install the generator before councils meter.

    I have to extend the 150mm cable which is armour cable (solid stranded copper) and I want to crimp onto this cable 150mm single core flexible cable ( braided copper cable), does anyone forsee any challenges with this?

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    I don' t see a problem as long as the core size fits the ferule correctly.
    We have had on numerous occasions had to use two different size lugs on a 4 core cable.
    You may end up using lugs and bolts to join through

  7. #17
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    Thank you GCE

  8. #18
    Site Caretaker Dave A's Avatar
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    Quote Originally Posted by FRENCHIE View Post
    I will send the pics once I get the know.
    The mobile site version doesn't deal with attachments particularly well. You need to work with the "desktop version".
    This may be an option with your browser (e.g. Chrome has it as an option).
    If it is an option in your browser, use this method to get to the desktop version as unchecking the tick box will get you back to the mobile version easily.

    Otherwise there is a View Full Site link at the bottom of every mobile version page.
    It works, but you are in for sport if you want to go back to the mobile version...

    Once in the desktop version of the thread -
    Click on Go Advanced in the Quick Reply area.
    Below the Post Reply area you can Manage Attachments.
    Click on that.
    Select and upload the image.
    Click Insert Inline
    You can close the pop-up and finish editing the post.
    Then Post Reply.

    (Looks complicated reading all that. Here's how the FAQ describes the process if you have trouble)

    One day when I'm bored, or in quarantine for Coronavirus I'll work on the Mobile Skin to make adding images easier that way...

  9. #19
    Diamond Member AndyD's Avatar
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    Quote Originally Posted by FRENCHIE View Post
    Hi Andi.
    I am working on my smart phone.............
    I've never use a mobile device to access the forum so I've asked for one of the other staff members to give you advice.

    Quote Originally Posted by SeanM View Post
    Greetings All

    I have to rectify a generator installation as the previous contractors install the generator before councils meter.

    I have to extend the 150mm cable which is armour cable (solid stranded copper) and I want to crimp onto this cable 150mm single core flexible cable ( braided copper cable), does anyone forsee any challenges with this?
    When you say braided copper' I'm assuming it's fine stranded wires...
    Just crimping with a ferrule is fine if the cable is glanded into an enclosure and joint is inside. Line tap connectors or DIN mount stud terminals would be another couple of options that have the advantage of being servicable in future. If the cable is trailing and you're jointing the cable with ferrules you should use a resin joint to give strain relief.

    DIN Mount Stud Terminals

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    Line Tap Connector

    Click image for larger version. 

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