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  • Users: QGeek
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  1. QGeek

    circuit protection for new branch

    I found a great article on sizing circuit protection for transformers and their loads: http://literature.rockwellautomation.com/idc/groups/literature/documents/in/1492-in001_-en-p.pdf In it, a helpful standard is listed: Circuit breaker protection for the primary side of the transformer can...
  2. QGeek

    circuit protection for new branch

    I need to modify a piece of equipment to include a circuit for an additional piece. The equipment is powered at 460VAC, 3-phase. The original equipment contains one step-down xfmr to 120VAC, and is protected by two primary and one secondary fuses. The add-on is 120VAC, nearly 10A max inrush...
  3. QGeek

    motor contactor terminals fused together

    Gents, I appreciate your time and input more than I can say. Have reached out to my customer/contact for more info. Will have a conversation and continue post with more details. Thank-you.
  4. QGeek

    motor contactor terminals fused together

    I have a report of two of the three motor phase terminals in a motor contactor being fused (shorted by melting) together. Twice in a row, same machine, same motor, same phases. This is on a machine in the field. I was thinking it could be a short in the motor windings. We are operating...
  5. QGeek

    fuse proximity to control transformer

    This is great, thanks. I will be well within bounds. I appreciate the assurance.
  6. QGeek

    fuse proximity to control transformer

    I am redoing a cabinet layout. We are using a different control transformer that is larger, and so the fuse holder that was formerly mounted on top of the transformer is being replaced by two DIN-rail mounted fuse holders (2P primary + 1P secondary). I am wondering what the proximity...
  7. QGeek

    motor softstarter troubleshoot

    Gents, I have just returned from the job site. I waited for two days with test equipment set up. Finally a fault happened. My hand happened to be on the joystick at the time. As I Extended the machine, it began to drag for maybe 2 seconds, before stalling and faulting. Same fault: Phase...
  8. QGeek

    motor softstarter troubleshoot

    Let me ask you this: what about the possibility of the contactor coil dropping out? To me this would more closely describe the fault: phase loss/open load. Is a contactor coil likely to drop out momentarily?
  9. QGeek

    motor softstarter troubleshoot

    I appreciate your help. Please let me know what further info I can provide. I have a lot. Here, for one, is the sfst sequence of operation, attached.http://files.engineering.com/getfile.aspx?folder=053fd51f-cfa2-48ee-92d4-ce8ab4a1df08&file=SMC-3_sequence.pdf
  10. QGeek

    motor softstarter troubleshoot

    wire 21 is +24VDC control power wire 22 is 24VDC common wire 31 is essentially 21 after the master control relay wire 32 is 31 after customer interlock relay.
  11. QGeek

    motor softstarter troubleshoot

    On the sfst, A1-A2 is control power and is on all the time (+24VDC). START is initiated by sending IN1 high (24VDC).
  12. QGeek

    motor softstarter troubleshoot

    Hi all. I have been working with a softstarter fault issue on my company's equipment for over a month now. The softstart is an Allen-Bradley SMC-3, and the fault is four-flash Phase-Loss/Open Load. I have initiated one fix so far, which initially reduced the faults entirely. What I suspected...
  13. QGeek

    460V equipment, 208V supply

    I feel truly enriched, can't thank you all enough. Plenty to go on (solve the problem), and plenty to look further into. Thanks again.
  14. QGeek

    460V equipment, 208V supply

    Ah! Thanks. The transformer I spec'd does say that it is suitable for "reverse wiring," which brings up a question I have had. What is it about transformers that would make them suitable for only one way? Would one need to look for a step-up vs a step-down transformer?
  15. QGeek

    460V equipment, 208V supply

    That is a great suggestion, thank-you! Any hangups I should look for in a step-up transformer? Interference issues stepping up from the 208V supply and then (for part of the equipment) stepping down to 120V inside the equipment, etc.?
  16. QGeek

    460V equipment, 208V supply

    Our machinery normally uses 460V, 3-phase supply. We have come across an instance where customer only has 208V, 3-phase, and not a hope of changing. I am in the process of converting the equipment. Someone suggested wiring the 460V motors in the delta configuration. Any advice?
  17. QGeek

    wiring question - practical

    I have a dumb question: In our control cabinet, we run several motors off the 3phase, 460V line. I need to add another branch circuit. I have the motor starter, reverser, motor, etc, but what do I do about the wiring? I've noticed that the terminals of the other motor starters use two wires...
  18. QGeek

    PLC test setup spike protection

    Really good suggestion, thank-you.
  19. QGeek

    PLC test setup spike protection

    I am designing a simple test setup with an Crouzet PLC. I am concerned about fusing and voltage spikes or bounce that would damage the PLC or other components, or give false reads on the PLC inputs. I have no control, at this point, over the PLC code. I would like to mimic as close as...

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