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  • Users: THooper
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  1. 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...
  2. 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...
  3. 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...
  4. THooper

    Help with a formula?

    Can anyone help me with figuring out a formula? Let me give you a brief background of my problem. We have been rewinding some dc traction motors for many years. We have a customer that lost eight of these motors off the same side of their car hauler. Each of the motor failures are classic...
  5. THooper

    Runaway armature?

    Can anyone help me with figuring out a formula? Let me give a brief background of my problem. We have been rewinding some dc traction motors for many years. We have a customer that lost eight motors off the same side of their car hauler. Each of these failures on the motors are classic runaways...
  6. THooper

    Why insulated bearings fail?

    I have a customer that has a new 200hp 449T,4-pole, 950vac belt drive motor. The customer said he has sent this motor back to the oem for premature bearing failure again (failed twice) in three months. The failure results of the bearing is evidence of electrical pitting in the bearing...
  7. THooper

    We are rebuilding a 350hp vertical

    We are rebuilding a 350hp vertical electric pump motor. The thrust bearing on the top end is a Kingsbury Babbitt thrust plate bearing. My question is, what finish should the machine finsish be? I was told by our machinest, Kingsbury bearings you need to surface grind the faces, and to grind them...
  8. THooper

    Vertical Motor ?

    Please share your experience on what can cause an up thrust on a vertical small deep well pump motor. Our facility rebuilt a 75hp 2-pole vertical motor only, a couple months ago and it was pulled for high vibration on the top end (thrust bearing end) After close inspection the lower guide...
  9. THooper

    Mounting Pinions

    Our electric motor repair shop installs a lot of pinions, we mount the pinion cold by placing it on the taper shaft by hand. Then we measure the COLD position of the pinion using a depth gage. We then remove the pinion and heat in the oven to 213F install pinion and measure pinion advance. The...
  10. THooper

    Motor Transportation?

    Good morning experts!!, I purchased a couple large new rebuilt 1500hp, ac ball bearing motors. When performing pre-testing we found that both motors have bad load end bearings and sound very rough. My question is, If the shaft has not been properly supported with a shaft bearing locking...
  11. THooper

    Accleration readings on 1250 hp

    We have recently acquired an SKF Microlog. We are to the point that we understand the microlog and the soft wear that goes with it. We are now starting to learn how to interpret the data. We recently rebuilt a 1250 hp, 1750 rpm, 2300 volt motor. The bearing arrangement is a NU228 in the drive...
  12. THooper

    Excessive brush wear

    We are working on a GE 300 hp DC motor. New brushes were installed in April and they showed 60% wear in a months time. Another set of brushes were installed and they had 50% wear in the last month. Concentricity has been checked on the commutator and there is about .001" run out. All of the...

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