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  • Users: noel0589
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  1. noel0589

    Rigid Work Schedule

    my last boss was the worst. he was an unrealistic old school asian workaholic. needless to say, i quit after a year. He said we could work on "flex-time" outside of normal 8am to 5pm. So I came in at 7am but when I tried to leave at 4pm, he says "flex time" doesn't mean I can leave early. It...
  2. noel0589

    Can a 3 phase motor start with power running in 2 phases

    Hi all, Just a quick simple question. I had a problem with an elevator and the contactor was returned to me. It looks like one of the poles is slightly damanged so it looks like the motor was probably single phasing, causing burn out. My question is can a motor even drive any load with only 2...
  3. noel0589

    AC to DC power converting generator failure

    But since the ac/dc motor generator failure coincided with the power outage, its hard not to draw any conclusion that doesn't include the fact that power integrity was not optimal. Maybe it was already in bad shape and maybe power did blink during the power outage causing an out of sync...
  4. noel0589

    AC to DC power converting generator failure

    yeah... that sounds like a reason. I don't really know why they are using power surge and outage together. When power is reapplied after an outage, is there usually an above normal surge of voltage/current? Is that a misconception?..or are surge protectors at home made to protect against...
  5. noel0589

    AC to DC power converting generator failure

    from pictures all I can see is that there was a turn to turn short in at least one coil
  6. noel0589

    AC to DC power converting generator failure

    Actually, the motor shop says it was due to a power surge, but a consultant is saying that it wasn't likely. So I was hoping someone might be able to shed some light. Thanks!
  7. noel0589

    AC to DC power converting generator failure

    Hi all, We had a failure of an AC to DC converting generator on the AC side. The failure coincided with a power outage. Would someone help give reasons as to how a power surge could have caused failure of the generator? Thank you in advance for any response!
  8. noel0589

    Motor Wire Sizing and the NEC

    Hi all, I have a question about motor wire sizing. NEC says we gotta follow table 310-16 if we will have motor wire in a raceway. However, it looks like our motor supplier provides leads that are smaller than NEC code would require in a raceway. It looks like they provided leads following table...
  9. noel0589

    Power Distribution and Excessive Voltage Drops

    So does it just mean that power can be "weak" (meaning voltage can drop more during motor start) not just between buildings but even within a building? Are there any remedies to this or is it just a "fact of life" type deal?
  10. noel0589

    Power Distribution and Excessive Voltage Drops

    Hi all, I was wondering if anyone could enlighten on the following. Why do some building power supplies have more voltage drop during motor starting than others? Lets say one 50HP motor causes momentary 5% voltage drop due to transient current surge during y-d transfer. Then lets say in another...
  11. noel0589

    Motor Circuit Analysis Equipment

    Hi all, Would anyone chime in on what they think is the best measuring equipment for motor and motor circuit analysis? I've seen some engineers at our sister factory with portable oscilloscopes that cost close to 10,000 dollars, but I think that's overkill for motors. Would a 300Mhz. bandwidth...
  12. noel0589

    star delta modified to Direct on line

    I still wonder about Y-D Open transition transient torque vs. DOL starting torque. What's worse? 1-2 cycles of auto reclose current / torque? or 5-6 cycles of starting current / torque. (5-6 cycles for motors I deal with) I didn't originally design the elevator systems I deal with using...
  13. noel0589

    Motor Starting Current graph analysis

    Hi all, I saw the subject on contactors come up again. http://rapidshare.de/files/1496465/hb.pdf.html Please download the above. Page 3 of attachment (hb.pdf) shows wye delta starting of a 40HP/200V motor using 208V/60Hz/3Phase power supply. Scale is 250A / div. (A) and 50ms/div (horizontal)...
  14. noel0589

    Motors, Starters, and Elevator Duty

    For a typical AC-3 Application, a certain sized starter, or more specifically, the contacts of the starter are tested to be good for 1,000,000 electrical operations under its rated application. And tests are done at a high frequency, almost 20-30 make/breaks per minute. However, for elevator...
  15. noel0589

    Supply voltage effects on motor current

    I have been looking around online and have come across a lot of contradicting information concerning motor characteristics under variations in voltage. According to G.E. if voltage is increased say 10% on a particular motor power factor will reduce by 4%, and full load current will decrease by...
  16. noel0589

    Supply voltage effects on motor current

    Thanks for responses, I've seen the voltage variation vs. motor performance curves. One thing is a little confusing to me, however. For a 230/460 V motor, which are the same motor, when voltage is increased from 230 to 460, there is a drop in locked rotor and full load current. However...
  17. noel0589

    Supply voltage effects on motor current

    Hi all, I'm trying to fill out a table for 3 phase ac induction motors. A 50HP motor has ratings of 148 full load amps and 808 locked rotor current at 200 volts. If power supply is 208 volts, I use a proportional equation which results in a higher locked rotor current (about 840)due to...
  18. noel0589

    Stator Winding Damage

    Hi all, For a 50HP 200V 3 phase wye-delta ac induction motor with class F insulation and FLA 148Amps and 1.0 service factor and 80 starts/hour rating (elevator duty): Is it possible to calculate insulation life/winding life/damage if motor is run occasionally above rated load for current of up...
  19. noel0589

    supply voltage effects and motor design

    Hi all, It is common motor knowledge that motor torque declines by the square of the change in supply voltage. However, there are motors designed for 230 or 460 volts, and torque is the same at all rpm for 230 or 460Volts, with only a change in drawn motor current. so in this case supply...
  20. noel0589

    Rotary Screw Pump, Submersible Motors

    Hi all, Thanks for the help. I am dealing with a submersible system of an electric motor driving a rotary screw pump which in turn drives a piston(plunger) which raises a hydraulic elevator system. Pump Data says that for pump to operate at 3400 RPM, the minimum flow rate must be 185.2GPM at...

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