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  1. #1
    llf264's Avatar
    llf264 is offline Cast Iron
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    My German lathe has three hot leads which I have figured out... and PE is the ground apparently... so what is N?

    I guess this brings me to another final question... what the heck is the difference ground and Nuetral.

    I know that code will be different in different places... but if ALL of my junction boxes, panels, machines, RPC's, and conduit on down the line are ALL connected back to ground bus (connected to the big white wire in the load center)is that a poor practice for a specific reason?

  2. #2
    peterh5322's Avatar
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    PE = (Protective) Earth (a guess, as you did not give the German word, and I'm not a German speaker).

    Neutral is a groundED conductor, and IS intended to carry ALL circuit "return" currents, but IS NOT intended to carry ANY circuit "fault" currents.

    G/E/PE is a groundING conductor, and IS NOT intended to carry ANY circuit "return" currents, but IS intended to carry ALL circuit "fault" currents.

    The groundED and groundING conductors are brought together at one point, only, within the premises ... at the service entrance panel.

    By segregating these two functions, as described, a fault in one machine or device cannot cause a dangerous condition in another machine or device.

    Certain appliances are specifically designed for "grounding through the neutral". To put this another way, these certain appliances are specifically designed for "grounding through the groundED conductor".

    In order to meet the requirements for "grounding through the neutral", the appliances must meet quite a number of additional safety factors, and each must be individually tested for compliance.

    The usual appliances are: kitchen cooking ranges, cooktops and ovens, and clothes driers.

    It is possible to convert an appliance which was designed for "grounding through the groundED conductor" into one which is suitable for "grounding through the groundING conductor". Cases where this is required include installations into manufactured homes, or travel trailers.

    It is NOT POSSIBLE to convert a device, such as a machine, which was designed for "grounding through the groundING conductor" into one which is suitable for "grounding through the groundED conductor".

    In most cases, machine tools do not use, and do not require a neutral, anyway.

    If you connect your groundING conductors to the groundED conductor (neutral) bus within your service panelboard, you are OK. This is not true in a sub-panelboard, however.

  3. #3
    llf264's Avatar
    llf264 is offline Cast Iron
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    Spot on Mate !! That solves that one as clearly as can be said. I always thought people were fat fingering the keyboard when they CAPSLOCKed the ED or ING at the end of the word ground.. I'll look for that distinction keenly next time.

    Many Thanks !!

  4. #4
    peterh5322's Avatar
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    "I always thought people were fat fingering the keyboard when they CAPSLOCKed the ED or ING at the end of the word ground."

    I believe I introduced that notation a number of years ago, perhaps here in this Forum.

    Later, I learned a few HTML tricks, and groundED could become grounded or grounded, and groundING could become grounding or grounding, but -ED and -ING works on all systems, and needs no help from HTML, so my use of these terms persists to this day.

  5. #5
    jim rozen is offline Diamond
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    Well, somebody else might have.

    Anyway, groundED is the white wire.

    GroundING is the green wire.

    In a european machine often, white = blue

    and

    black = brown.

    green = green/yellow stripey.

    The idea that all US service relies on is,
    if there is a fault at a machine, and fault
    current flows from the hot lead to machine
    frame, enough current will flow to trip the
    overcurrent protection at the panel.

    This is how personal protection was originally
    concieved. For it to work you need to basically
    have two things:

    A separate low impedance path from the machine
    frame to the panelboard, and it has to be a
    conductor sized to carry the *full* current
    needed to trip the overcurrent protection. If
    those two things are present then the frame
    of the machine will not rise up much in voltage
    before the breaker trips off.

    Nowadays GFIs have changed the landscape a bit
    but the green/white wire plan still works pretty
    well. With those (gfi's) there is a continous
    comparison between the black wire current and
    white wire current. If they differ, the
    difference is assumed to be fault current and
    the GFI trips off.

    More mnemonics:

    WHite wire = _W_ide blade on receptacle

    Black wire = _B_rass screw on receptacle.

    As time goes on, the code exceptions for shared
    ground/neutral conductors are going away.

    One place you *will* find a second "bonding"
    point in a service (bonding is when the
    white and green wires are tied together) is
    at the secondary of an isolation transformer,
    often used in machines to provide control power.
    In that case the secondary winding is called
    a 'separately derived service" and as such
    *must* be bonded to ground. So you will
    see the secondary winding tied to chassis there,
    and a new white wire pick up at that point
    to run the control circuits.

    Jim

  6. #6
    JST's Avatar
    JST
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    It is NOT POSSIBLE to convert a device, such as a machine, which was designed for "grounding through the groundING conductor" into one which is suitable for "grounding through the groundED conductor".
    But I'll bet quite a few people have converted 220 dryer type circuits to 220 machine circuits, and have used the shield/neutral for groundING.... without moving it to the ground bar.

    Not code, but works so long as the bonding in the panel is good.........

  7. #7
    llf264's Avatar
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    I'm proud of myself for terminating my white lead and the blue terminal (N) on the machine and my green lead on the green/yellow stripey (PE) (green/yellow stripey being my term exactly all afternoon too though I do have my three black leads (L1,L2,L3) going all the black leads on the machine. I checked and thier L1, L2, L3 are all black as well.

    The voltage supplied varies between 404 and 408 so I am within 2.5% of 400v on the output side of the transformer. Tolerance per the factory (at 60Hz) is +/-10% so it looks like things are getting close to ignition time.

    My last question now is (which also coincides with my other post about the X0 taps) the Nuetral (white) lead at the load center is connected directly to the machine's Neutral (blue) without ever going through the transformer....

    If the three hot leads to the machine are 400v, and the Machine's N line is connected to the load center's N Line then isn't there a voltage imbalance?

    I'm sitting back, looking at things and thinking to myself it would be a bad idea to throw the switch right now.

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    peterh5322's Avatar
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    If you're using a transformer between your panelboard and your machine, you must crate a "separately derived" system, at your machine.

    Most distribution transformers do not have a neutral for their primaries, but do for their secondaries.

    In order to create this "separately derived" system, run the neutral to the machine's groundING terminal.

    When a transformer has an H1, H2 and H3 for the primary, it often has an X0, X1, X2 and X3 for the secondary, and X0 is most often the neutral.

  9. #9
    llf264's Avatar
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    I do have two X0 taps at the top of the transformer on the same bar... but then my ground would violate the groundING groundED rule would it not?

    Attached is a wiring diagram as it sits this moment.


  10. #10
    llf264's Avatar
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    So, to create this seperately derived system, and the GY (Protective Earth) on the machine is connected to X0 on the secondary side of the transformer, where does the Neutral line on the machine go?

    And how/where does the X0 tap return the power is receives (if it ever gets a fault)?

    I don't think that I am following this one properly.

  11. #11
    llf264's Avatar
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    I think this is where we go from delta to wye... 3 wire to four wire via the isolation transformer, is that correct? And that only thing I change on the diagram above, is to connect the blue Neutral from the Machine to the X0 tap at the top of the transformer?

    If that assumption is wrong, then disregard the next question, if it is correct, then how does the whole delta to wye "conversion" happen?

  12. #12
    JoeFin is offline Stainless
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    If you are installing a transformer in your shop – the secondary ground point will serve as the Neutral Bonding point.

    Go to the rental yard, get one of those big electric “Hammer Drills” and drill a hole completely through the concrete slab within 6” of the foot print of the transformer. Then use the hammer drill to drive a 10’ x ½” Gnd all but 6” into the ground. That becomes the Service Gnd point and where you will bond the secondary Neutral.

    Important NOT to run or attach a primary side Neutral. Also attach the Primary side Gnd to the Transformer case – NOT the new Gnd rod

    Hope that helps

  13. #13
    peterh5322's Avatar
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    Consider the two cases:

    1) your utility service, with its transformer located somewhere outside your premises, and

    2) your lathe's step-up transformer, with its transformer located near the lathe.

    In case (1), you create a system at the service entrance panelboard, which is the closest point within your premises to the utility's transformer.

    In case (2), you create another system at the transformer itself, which is the closest point within your premises to that transformer.

    The G conductor still runs from your panelboard to the transformer and to your lathe.

    The transformer's W conductor (X0) runs to your lathe, but it is bonded to G within the transformer's connection box.

  14. #14
    Modelman is online now Stainless
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    This is how personal protection was originally
    concieved. For it to work you need to basically
    have two things:

    A separate low impedance path from the machine
    frame to the panelboard, and it has to be a
    conductor sized to carry the *full* current
    needed to trip the overcurrent protection. If
    those two things are present then the frame
    of the machine will not rise up much in voltage
    before the breaker trips off.
    Which is why it is so important to ensure continuity all the way back to the earth ground, otherwise a fault in one machine can affect any other that is tied to the “floating” ground wire.

    I had an interesting experience years ago on a construction site. Any time I would pick up a power tool, any power tool, I would feel a tingle. No one else did, but I was still wet behind the ears, and had softer hands, I guess. Anyway, when I complained to the foreman, he looked at the plug, confirmed the ground prong was there, and told me I was full of it. When I persisted, he bent down and triggered a saw to show me that everything was perfectly fine, at the same time getting his legs around a piece of re-bar sticking out of the deck. Yeowee! He had the electricians running all over that job site that afternoon. Turns out the excavator’s bulldozer had ripped the cable off the ground stake at the temporary service, and one tool with faulty insulation was enlivening the case of every tool on the job.

    Dennis

  15. #15
    llf264's Avatar
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    I have updated the wiring diagram above to reflect the current state of wiring as t sits.

    Can you take a look at this and tell me if this is what you are talking about?

    The only thing that I don't have is a new ground physically plunged into the ground. Is that really neccessary before throwing the switch?

    Is it ready (my liability completely with no-one else involved) to test to see if I have power to the machine? or is there a bit left to do?

  16. #16
    peterh5322's Avatar
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    Looks to me as if you have the bases covered.

    The groundING conductor has been brought back to the source panel, and you have created a "separately derived" system between the transformer and the machine which it immediately serves.

  17. #17
    llf264's Avatar
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    I won't be able to physically test the system till next Friday night as I'm out of town till then.... and I feel comfortable with that I've learned so far.

    I'm just having a hard time figuring out the fundamental difference between single phase AC and three phase AC treat Neutral. Where was the name Neutral derived?

    If it carries current one way then the other in single phase (hence the name "Alternating") as a slave so to speak from the hot wire (black), does that mean that the power company reverses the current flow on the black lead and the "Neutral" is just the conduit which goes whichever way the black lead "pushes" or "pulls" it?

    Right now, that is the only way I can justify Neutrals exhistance, in my mind, in a three hot phase system... that is to say as a "slave" of the other three hot leads, or does the power company alternate the "direction" of the current in both the Hot and the Neutral simultaneously and it's more like two people on the end of a saw blade pushing back and forth with equal power simultaneously.

    Basically, I'm trying to figure out Neutral's "purpose" in life as "half" of a single phase system, and a "fourth" of a three phase wye system. Because come to think of it... in three phase Delta, the Neutral line doesn't even exhist does it????!!

  18. #18
    peterh5322's Avatar
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    Three cases to consider:

    1) North American 120 or 120/240 single-phase system (the neutral is the "return" conductor, a current carrying conductor, carrying the same current as the ungrounded conductor),

    2) North American 240 or 480 three-phase ∆ systems (there is no neutral conductor, so no "zero sequence" currents can flow), and

    3) North American 120/208 or 277/480 three-phase Y systems (the neutral is a current carrying conductor, but it usually doesn't carry any current attributable to connected three-phase loads unless there is an imbalance, and then this current is a "zero sequence" current, however the neutral does carry any return currents attributable to connected single-phase loads).

    Does your German lathe really require a neutral?

    Even if it doesn't, you would still connect X0 to G in order to create a "separately derived" system.

  19. #19
    Dag S K is offline Aluminum
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    Moast of this is possible to pick from the earlier replies.

    In Europe the N(eutral) conductor is commly blue.
    (white may be live) The N on a 400V 50Hz system is always connected to the center of the Y.
    Ususally, but not necessarily,the PE (protective earth)is connected to the N at the trafo, and usually later at each first fuse panel in a house.

    When running a 400V 50Hz motor on 60Hz, the voltage should be encreased by 6/5 to approx 480V.

    BUT! The single phase equipment may not accsept the rised voltage. Eg. a power supply putting out 24V DC, or some coils.

    The setup in dhe diagram above will probably do well. (motors ar usually oversized) The bonding between the transformers N and PE is only ok if the transformer not is an autotransformer.
    The unit shall work well without consern of voltage between N and ground.

    Keep an eye on eventually high temp on the motor etc.

    This may help to:
    http://en.wikipedia.org/wiki/Earthing_system

    dsk

  20. #20
    jim rozen is offline Diamond
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    The term 'neutral' is of course not exactly the
    best one though it is used commonly.

    Truly correct for single phase in the US would
    then be, as mentioned before,

    GroundED conductor. This is the load carrying
    wire which is connected, at the panelboard, to
    the chassis of the box. It is supposed to carry
    load current.

    The answer to the question about 'is there a way
    for fault currents in the diagram above to
    get back to the service entrance' is a resounding
    YES because you have tied the chassis of your
    lathe to the chassis of the transformer which
    is then tied back through green wires to the
    service entrance. Further the secondary of the
    transformer is BONDED to ground so there is a
    path for fault currents to flow via that green
    wire that goes over the top of the transformer.

    Jim

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