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  1. biggeorgetechnical

    choice among two theories for a random winding turn failure

    Dear electricpete, I was wondering: How sure are you that surges were essentially absent? Do you have some kind of scans on the voltages? Thanks, George "When you go looking for problems, you will find them... But they may not be the problems you went looking for!"
  2. biggeorgetechnical

    Electric motor insulation drop after cleaning

    In my experience, these surge results would tend to indicate leakage between the turn-turn or phase-phase insulation is now present. (A quality DLRO would allow you to detect if it is a dead short) Based on the info discussed in this thread, I'd suspect that contamination might have washed into...
  3. biggeorgetechnical

    Surge Comparison Test

    Hello, A few questions for workshop supervisor should be: A) Why did they select 1500V for the test voltage on the incoming tests and analysis? B) What other tests were performed? i.e. visual inspection, DLRO, meg-ohm, etc, etc. c) Why did they select 5000V for the outgoing quality control...
  4. biggeorgetechnical

    Delta connected motor failing surge test ????

    electricpete seems to be suggesting testing at lower voltages, gradually increasing the voltage - to see if the separation "comes on" as the voltage is increased. This is a suitable method to use. This is a different technique than comparing at the full "Surge comparison" test voltage. Baker...
  5. biggeorgetechnical

    motor burnout from pressure washing

    Dear Airsmybag, If you are already meggering these motors after your cleaning work, disregard this post. For the future - as you still intend on staying in this line of work, right? I suggest you might want to megger the motors before restart. Its possible/even likely this liquid...
  6. biggeorgetechnical

    Simple question, not so simple to find answer?

    Being an electrical guy, these civil and mechanical concepts are tough for me to wrap my mind around. Here is one explanation I have been able to find. http://www.pat2pdf.org/patents/pat20090044482.pdf Link "When you go looking for problems, you will find them... But they may not be the...
  7. biggeorgetechnical

    Simple question, not so simple to find answer?

    Like I said, I cant visualize how its actually done, maybe its "just the way it was patented" or something obscure like that? "When you go looking for problems, you will find them... But they may not be the problems you went looking for!"
  8. biggeorgetechnical

    Simple question, not so simple to find answer?

    These are post tensioned anchors. But after a bit more research myself, I think there is little doubt RossABQ has provided the answer. Never having been present at the building of such a base, I cvisualize how the process is actually performed. "When you go looking for problems, you will find...
  9. biggeorgetechnical

    Simple question, not so simple to find answer?

    Maybe BigTomHanks is on to something. I looked up a couple wind turbine base patents, and the ~64 large left hand bolts pass through a massive base of concrete, to a ring on the bottom side of the base. Can't tell if the other end of the re-bar is right hand thread. But, one of the stated...
  10. biggeorgetechnical

    Simple question, not so simple to find answer?

    Thanks! "When you go looking for problems, you will find them... They may not be the problems you went looking for!"
  11. biggeorgetechnical

    Simple question, not so simple to find answer?

    Interesting. But, I thought it might have something to do with the yaw controls or something twisting the tower and they were this way to resist it. Maybe its just as simple as you suggested. "When you go looking for problems, you will find them... They may not be the problems you went looking...
  12. biggeorgetechnical

    Simple question, not so simple to find answer?

    Question: I am wondering why the bases of the large wind turbines I toured recently had something like 64 large, "left hand" thread bolts in the base. The tour guide did not know, but he did say they were torqued to something like 2000 lbs. Why the '"left hand threads? Thanks, George
  13. biggeorgetechnical

    Dust removal from stator and rotor

    Hi, I spent a week recently at an industrial facility in a desert climate, and dust penetration into rotating equipment was stated by staff to have been a bit of a challenge. Multistage filters are used, but with frequent dust storms become reduced/plugged relatively rapidly. (There is a...
  14. biggeorgetechnical

    VSD outout is erratic in no load test only.

    ahendawy85 You will likely need a Fluke 289 or equivalent, this has the low pass filter. I agree with Skogskurra. To make any judgement about the output transistors, my advice is to use a suitable oscilloscope with appropriately rated probe(s) George www.edeinst.com
  15. biggeorgetechnical

    Partial discharge in VFD driven 400V motors, does it really exist?

    I am wondering if any forum members can share their knowledge on this subject? There was a lot of discussion on VFD spikes/mitigation recently in thread titled "Terminator networks for VFD" Can these spikes create enough electric stress to generate ozone in a low voltage induction motor?
  16. biggeorgetechnical

    PIN diode limiter - or TVS's ?

    Thanks for the comment, To try and answer your question, this is a 2 pole high pass, the coils are designed to offer a 3db point of ~100Mhz, according to the physical dimensions. It's intended to be (appears to act quite nicely)a broadband high pass detector. For example it readily detects a...
  17. biggeorgetechnical

    PIN diode limiter - or TVS's ?

    I have a 2 pole T network, as a high pass. The network feeds a Dc biased Schottky diode that is acting as the RF burst detector. These RF bursts are generated as transients due to sparking activity, generated by high voltage spikes. For detection purposes, It is working very well, but sometimes...
  18. biggeorgetechnical

    Motor Testing Equipment

    billybry, Back to the original thread, regarding advantages of AT31: A gentleman I know works for a large Aluminum mill. In his job there are 1000s of motors to be tested on a regular basis. He is very skilled, and well equipped with most (if not all) the brands mentioned in this thread. He...
  19. biggeorgetechnical

    Motor Testing Equipment

    I have looked at the above links to BJM and Electrom websites. I feel compelled to post the link to the above mentioned Baker website. It looks like it has quite a bit of information on it regarding high potential testing, surge testing in general, as well as a series of documented case studies...
  20. biggeorgetechnical

    Motor Testing Equipment

    billybry, The tool you are asking about incorporates several measurement techniques into one box. I'd like to mention that there are many additional motor test capabilities integrated into modern surge testers. Newer surge tester boxes often incorporate: Kelvin Resistance Bridge, Meg-Ohm...

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