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  1. THooper

    Rotor bar melt down

    We need to verify as you stated on the overload protection. I don’t know what measures were taken that brought them to the conclusion that they are working fine. As far as being loaded and starting under load is very possible, but I am told it is not, that it is started and left running and...
  2. THooper

    Rotor bar melt down

    Rotor slot configuration:http://files.engineering.com/getfile.aspx?folder=d98fdc13-ef3b-4017-a359-524289fc874e&file=slot_configuration
  3. THooper

    Rotor bar melt down

    June stator failure:http://files.engineering.com/getfile.aspx?folder=3ad5b15f-82da-4242-b06a-aaf19f960e93&file=stator_june_failure.bmp
  4. THooper

    Rotor bar melt down

    June rotor fauilure:http://files.engineering.com/getfile.aspx?folder=afe92f8c-3648-44ac-bc44-c4c5d709f72d&file=June_failure.bmp
  5. THooper

    Rotor bar melt down

    The application is a small crusher, called a feeder breaker used in an underground coal mine. Most the information I have thus far is from the Maintenance Coordinator whom says all overload protection is working fine and they have not stalled it out, that they (manual) start it at 7:00am and it...
  6. THooper

    Rotor bar melt down

    Below is failed rotor image.http://files.engineering.com/getfile.aspx?folder=8af1fd1a-b2d7-4a98-979f-7858ed615fda&file=rotor.bmp
  7. THooper

    Rotor bar melt down

    Below is failed motor image.http://files.engineering.com/getfile.aspx?folder=a8cb05ae-9be8-40e1-948e-815d0b74c6ad&file=150.bmp
  8. THooper

    Rotor bar melt down

    Please give your expert opinion on the photos below. This motor failed due to open rotor bars after several years of service in June. The bars on the failure in June were at the end ring connection point and appeared to be from fatigue. The rotor was re-barred by a rotor re-bar facility, after...
  9. THooper

    AC motor turn into a generator..

    We have four 250hp ac motors running in tamdom on a belt drive, controlled from VFD's If one of these motors was unwired and left "coupled up" and would still rotate at 1800rpm driven from the other three motors, would this unpowered motor possibly produce any voltage? I have read that it takes...
  10. THooper

    Motor inertia information

    www.reliance.com/mtr/aplel.htm
  11. THooper

    Motor inertia information

    A load which tends to cause the motor shaft to continue to rotate after the power has been removed (stored kinetic energy). If this continued rotation cannot be tolerarted, some mechanical or electrical braking means must be applied. This application may require a special motor due to the energy...
  12. THooper

    Pin point failure anaylsis / root cause

    I should of elaborated a little more on my thoughts of possible mag center problems. Not real common but I have repaired probably a dozen motors in the past sixteen years where the rotor core had moved on the shaft enough to cause a constant preload on the load end bearing causing the bearing to...
  13. THooper

    Pin point failure anaylsis / root cause

    If your rotor alignment is off when the motor is under load, it will try to pull and get mag center and cause pre-load on the bearing, rotor iron should be longer than stator iron. Use the advise of cutting the bearing in half for inspection along with pre vib readings, temp readings etc...
  14. THooper

    TROUBLESHOOTING THREE PHASE CABLE

    BJC Did bring up a very important point, we are supplied with methane detectors and by law we have to take CH4 readings every twenty minutes while working in the face of the mine where methane levels are common. It is also required to perform CH4 tests before any welding or torches can be used...
  15. THooper

    TROUBLESHOOTING THREE PHASE CABLE

    Thanks for the ebay tip, I just bought a brand new crank 500v megger for $70.00 off ebay using the buy it NOW! Thanks again guys
  16. THooper

    TROUBLESHOOTING THREE PHASE CABLE

    Hello experts, I am a past electric motor winder and builder. I just took on a new job in the coal mining industry. The testing equipment supplied is limited. They do not have meggers, hypots or surge testing equipment that I am more comfortable using for troubleshooting at my past job. I am...
  17. THooper

    Help with a formula?

    They extend the same amount as the oem print, We also add a surge rope to the coil head during the winding process that is not oem, I did not mention previously because I was unaware of the surge rope, but this should also add to the strength. I am researching the spec's on the surge rope also.
  18. THooper

    Help with a formula?

    The winding have expanded so far they show tearing of the banding and insulation. We are talking about running one up past rated rpm to see when it comes apart, but have not done so as of yet.
  19. THooper

    Help with a formula?

    Yes, the armatures go through a vpi process, vacuum pressure impregnation. The coils are staying put in the iron slots, but flaring and mushrooming as they exit the core iron of the armature.
  20. THooper

    Runaway armature?

    This is good information to know and look at, I will get more details as you have describe, I also posted this in Mechanical Engineering and other topics, which also had some good input. thanks again aolalde!

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