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  1. joepower

    4 kV Motor Shoots Fire and Sparks on Startup but Still Runs

    Thanks for the input - even though the rotor passed a growler test and all other routine tests and was ready to ship from teh repair shop, I had them run it up to about 1100 HP load and watch it with their MCE tester. An anomoly did show up in the rotor and I am waiting for details.
  2. joepower

    4 kV Motor Shoots Fire and Sparks on Startup but Still Runs

    On several occassions it was noticed by operators that a 1750 HP compressor motor shot "sparks" or "fire" out the back when it started. The motor is open frame. After starting the motor would continue to run, at times for over a week before being shut down based on system...
  3. joepower

    Westinghouse 150-DHP-500 Breaker

    My catalogs show that Westinghouse listed the breaker as both 23 and 25 kA symmetrical at various times. The 1979 and 1985 C37.09 standards called for a 28 kA symmetrical rating: http://www.joepower.com/toolbox/cbrating/cbrating.htm It's not a simple question...
  4. joepower

    Repair vs Replacement policies

    Try the flowchart at http://www.easa.com/indus/rr0601.pdf
  5. joepower

    Simultaneous 4kV Motor Failures

    The multiple electrical failures in the 6000 HP motor were generally "in the slot", or phase to ground rather than phase to phase. The rub marks seen in the photo are interpreted by the rewind shop to be wear marks from an abrasive dust environment, although I still need some...
  6. joepower

    Simultaneous 4kV Motor Failures

    A picture of the failed 6000 HP motor is at: http://www.joepower.com/misc/MVC-006F.jpg A diagram of the surge suppression setup is at: http://www.joepower.com/misc/motor.jpg Both the metal-oxide surge arresters and capacitors are rated for use on a high resistance groudned system. Capacitors...
  7. joepower

    Simultaneous 4kV Motor Failures

    Awesome input. I should be at the motor repair shop tomorrow to get the full report on the nature of the failures. I'll post some of the digital pictures to my website as soon as I get them.
  8. joepower

    Simultaneous 4kV Motor Failures

    It is broken delta, and the resistor is in parallel, but teh relay is called out as a 64. However, it appears from further research that only the transformer neutral ground was in the circuit as the bus tie to teh section of gear with the broken delta configuration was open and the buses were...
  9. joepower

    Simultaneous 4kV Motor Failures

    Original poster here. For the high resistance grounding, the transformer feeding the bus has a single 10 kVA, 1-phase, 4160/120V transformer in its neutral with a 0.866 ohm, 8 kW resistor on its secondary with a 64 relay. The bus the motors are fed from has a similar setup but with three...
  10. joepower

    Simultaneous 4kV Motor Failures

    The motors were running under normal full load conditions when the event happened with non other switching. No major system changes have been made since the system was designed or the surge protection added. There are no harmnonic generators on the system such as VFDs. Both motors did fail...
  11. joepower

    Simultaneous 4kV Motor Failures

    We experienced the simultaneous failures of two 4kV fan motors on a high resistance grounded system. They were on the same switchgear bus, a 6000 HP fan (located outside) and a 600 HP fan (inside) – both less than 300 feet from the bus. The 6000 HP fan has surge protection at its terminals –...
  12. joepower

    Preperation for power engineering position interview

    To answer you better, it helps to know the type of position that you are looking for - some such as electric utility system planning and stability studies require academic moxy, while most power engineering positions require an ability to order the right equipment and get it to work when it...
  13. joepower

    480V Molded Case Breaker Position Verfication

    Regarding my statement that it may not be safe to be checking voltage at the load side of the breaker, the issue is similar to a typical 15A molded case breaker which is not rated/tested to interrupt at its load side terminal, there is always a minimum amount of wire in the UL test circuit . See...
  14. joepower

    480V Molded Case Breaker Position Verfication

    Molded case breakers in motor control centers are often operated indirectly by an external handle on the front of the MCC cubicle. As the mechanical linkages wear over time and the original circuit breakers are replaced with breakers that are not dimensionally identical, how do you ensure...

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