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Thread: 6 lead motor & VFD

  1. #1
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    6 lead motor & VFD

    We are attempting to connect a 6 lead 460 volt 100 HP part winding motor to a VFD. We connected leads 1 & 7 to T1, 2 & 8 to T2 and 3 & 9 to T3. We are getting fault codes on the drive and was told that the breaker in the panel tripped when the drive was put in bypass. I'm wondering if this motor and drive are compatible or if we have the motor wired correctly?
    Joe


    "The Difficult we can do, the Impossible just takes a little longer"

  2. #2
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    At first glance I'm wondering why, if it's a six-lead motor, you have leads numbered above six. I have no experience with part-winding motors but I don't believe you can connect one to a VFD.
    Deserve's got nothin' to do with it.

  3. #3
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    I've seen 3, 9, 12 lead motors but I don't recall ever seeing a six lead.

    We always wire part wind start motors to the RUN diagram when using a VFD. I googled and didn't get any noticeable hits for 6 lead. My ugly's only shows 9 lead motors too...

  4. #4
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    Quote Originally Posted by Cow View Post
    I've seen 3, 9, 12 lead motors but I don't recall ever seeing a six lead.
    Reasonably common for wye-delta, single voltage ... but part winding ... I'd really like to seen the motor schematic.

  5. #5
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    Has this motor been modified at motor shop?
    Tom
    TBLO

  6. #6
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    Quote Originally Posted by joebell View Post
    We are attempting to connect a 6 lead 460 volt 100 HP part winding motor to a VFD. We connected leads 1 & 7 to T1, 2 & 8 to T2 and 3 & 9 to T3. We are getting fault codes on the drive and was told that the breaker in the panel tripped when the drive was put in bypass. I'm wondering if this motor and drive are compatible or if we have the motor wired correctly?
    Are you sure it's part winding?
    Most of the six terminal motors I've seen have had both ends of the three stator windings brought out to terminals. This allows the motor to be connected in either star (wye) or delta. Can be used for Star-delta starting or for two different operating voltages.

  7. #7
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    Most likely this is a semantics issue. "6 lead" technically means that there are six leads INSIDE OF THE PECKER HEAD, but you only bring 3 wires into it from the starter. On a Part Winding start configuration though, you bring 6 wires into it from the starter, but usually there are 9 or 12 "leads" inside of the pecker head. From the wire numbers, I'd say it is a 9 lead motor. Sometimes even if it is technically a 9 lead motor, you may only be able to see 6 of the 9 anyway, especially on older motors.

    To make that work with a VFD supply where you are only going to bring 3 wires in from the VFD, you need to combine the two sets of windings. Look at this diagram:




    For connecting a VFD, imagine that there are no contactors and each pair of wires must go to the VFD cables. So from this is looks as though you did it right, 1-7 to L1, 2-8 to L2, 3-9 to L3. But here is the caveat...

    This diagram is the NEMA standard. Unfortunately not everyone uses the NEMA standard for Part Winding motors. In this drawing, 4, 5, and 6 are internally connected together to form the Wye (but as I said you may or may not be able to see them). I have seen some where 6, 7, and 8 are used instead of 7, 8 and 9, and the internal Wye ends of both sets of windings are all called "9" because they are all common to each other. Sometimes in that configuration, you will see 6 wires all with a number 9 on them, sometimes it is internal and you don't see them at all. We can't see your pecker head connection diagram. Does it look like this?

    If this does look like your diagram, are you using a breaker that came from the old PW starter? Because if so, it might be too small to work for an Across-The-Line bypass. Technically, PW starters are supposed to have separate breakers (or fuses) for each set of windings, although that was a late change in the code and there are still a lot that do not. But if yours was one built to the newer standards and you are only using only one breaker, it may not be able to hold in under A-T-L inrush current.

    As to the VFD faults, are you trying to use Vector Control? If so, did you perform an auto-tune? If not, VFD default settings for the motor parameters would not take into account the differences in the motor between standard and PW connections. Auto-tune would (should) have picked that up. If you are just running it n V/Hz mode, it should not have cared.

  8. #8
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    Should also mention 2 more things:
    1. If it's a 12 lead motor, all of the above is out the window...
    2. Not all motors with 6 connection points are Part Winding, could just be dual voltage or Y delta.

  9. #9
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    Quote Originally Posted by Jraef View Post
    Most likely this is a semantics issue. "6 lead" technically means that there are six leads INSIDE OF THE PECKER HEAD, but you only bring 3 wires into it from the starter. On a Part Winding start configuration though, you bring 6 wires into it from the starter, but usually there are 9 or 12 "leads" inside of the pecker head. From the wire numbers, I'd say it is a 9 lead motor. Sometimes even if it is technically a 9 lead motor, you may only be able to see 6 of the 9 anyway, especially on older motors.

    To make that work with a VFD supply where you are only going to bring 3 wires in from the VFD, you need to combine the two sets of windings. Look at this diagram:




    For connecting a VFD, imagine that there are no contactors and each pair of wires must go to the VFD cables. So from this is looks as though you did it right, 1-7 to L1, 2-8 to L2, 3-9 to L3. But here is the caveat...

    This diagram is the NEMA standard. Unfortunately not everyone uses the NEMA standard for Part Winding motors. In this drawing, 4, 5, and 6 are internally connected together to form the Wye (but as I said you may or may not be able to see them). I have seen some where 6, 7, and 8 are used instead of 7, 8 and 9, and the internal Wye ends of both sets of windings are all called "9" because they are all common to each other. Sometimes in that configuration, you will see 6 wires all with a number 9 on them, sometimes it is internal and you don't see them at all. We can't see your pecker head connection diagram. Does it look like this?

    If this does look like your diagram, are you using a breaker that came from the old PW starter? Because if so, it might be too small to work for an Across-The-Line bypass. Technically, PW starters are supposed to have separate breakers (or fuses) for each set of windings, although that was a late change in the code and there are still a lot that do not. But if yours was one built to the newer standards and you are only using only one breaker, it may not be able to hold in under A-T-L inrush current.

    As to the VFD faults, are you trying to use Vector Control? If so, did you perform an auto-tune? If not, VFD default settings for the motor parameters would not take into account the differences in the motor between standard and PW connections. Auto-tune would (should) have picked that up. If you are just running it n V/Hz mode, it should not have cared.
    Thanks this is very helpful, The label on the inside of the motor housing is stating that this is a "Part Winding" motor and is basically showing the same wiring diagram that you posted.Tthe start up was in bypass but I do not believe it was across the line but more of a V/Hz. I learned late last night that this motor has been sitting in this penthouse for about 6 years before we installed it, don't know if that makes any difference one way or the other.

    Thanks Again.

    Joe
    Joe


    "The Difficult we can do, the Impossible just takes a little longer"

  10. #10
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    sounds like a single voltage part start and your connection is correct. Whose brand is it? Also if the drive was hooked up and the motor started fine on the vfd say on a lower setting and then the speed was increased and all was ok that sounds righ. Then if you put it in a bypass mode and tripped the breaker its possible that the breaker size is not high enough to get the motor started when started across the line. Make sense?

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