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  • Users: gordonl
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  1. gordonl

    Acceleration affects on fan

    I've been doing the electrical investigations on the use of a VFD on a 3500HP induced draft fan. We would be cycling the fan between full speed and base speed (approx 20%) several times an hour. Currently the fan is dampered back several times an hour, but with the VFD we would ramp the speed...
  2. gordonl

    Vibration detection for blades in turbo machinary

    This is also posted in "Mechanical - Vibration" Forum, but thought I would post here since motor experts are often also the vibration experts: I'm looking at reusing the existing proximity sensors on a steam turbine driven axial compressor for a new monitoring system. There are 4 sets of x-y...
  3. gordonl

    Vibration Monitoring on a Steam Turbine and Axial Compressor

    I'm looking at reusing the existing proximity sensors on a steam turbine driven axial compressor for a new monitoring system. There are 4 sets of x-y probes, one set on each bearing, a thrust probe, and a key way probe for speed and phase. Is there any value in having accelerometers added to...
  4. gordonl

    Vibration Monitoring - How far do I go?

    We have 2-16MVA turbo generators and 3 turbo blowers similar size. About 10-15 years ago our insurance company requested we install a vibration monitoring system, which has since given up the ghost. We have solicited proposals for new systems using the existing sensors and the proposals are...
  5. gordonl

    Suppliers of Static Exciters

    I'm looking at changing rotating exciters and old pot style voltage regulators with new static exciters on two 11kV 20MVA turbo gen machines. (600A Field Packages) Any suggested suppliers (North American), I already have some info on C-H's offering. As well I would be interested in hearing...
  6. gordonl

    Low Volatge Circuit Breaker Reliability

    I'm looking at replacing an old 600V switchgear lineup with a new or refurbished lineup. My question: Is there any sourcs of data that compare ANSI breakers from different manufacturers for reliability? IE trip unit failures, false trips, breaker failures, etc. Our first foray into the market...
  7. gordonl

    "Weird" Application of Line Differential Protection

    Let me first describe the application: 35kv shielded cable, direct buried approx 1km, 6-1C-500MCM. Line differential relays are 3 element, dual fiber channel, with integrated overcurrent and distance protection. My system has a fault level of about 20KA symetrical, and the system is...
  8. gordonl

    Frequent Starting of Low Inertia Loads

    I have some 500 & 1000HP water pumps which I am considering changing over to an automated start stop system. These motors pump cooling water which is only required between about 1 minute every 7 minutes, to 1 minute every 18 minutes depending on the process. The motors start in about a tenth...
  9. gordonl

    Affect of Soft Starters on Motor/Rotor Heating

    I'm wondering if a start of a load using a soft starter is easier on a motor from a thermal capacity point of view compared to a DOL start. I realize mechanically it is easier on the motor, but will the use of soft starters improve the number of starts a motor is capable of?
  10. gordonl

    Arcing in MCC

    I've recently had an MCC tub arcing at the bolts which fasten the tub to the frame. We found that the tub grounding system was quite poor so we added grounding jumpers to each tub. We couldn't find anywhere on the tub, front or back, where there had been a phase to ground fault, and the...
  11. gordonl

    Plating in Corrosive Atmospheres

    I'm interested in hearing the experience of others with types of plating used in SO2 enviroments, (IE tin vs. silver) as well as other types of protection used.
  12. gordonl

    Neutral Grounding Resistor Protection

    We use a large amount of low resistance grounded MV systems, the only protection currently is graded ground overcurrents. A company has recently brought to my attention their NGR monitors which monitors the banks resistance with alarm for increased resistance. (Also incorporates overcurrent)...
  13. gordonl

    Snaking Direct Buried Cables

    What is the typical measure for quantifying the amount of snaking in direct buried cable, and what are some of the values typically used. Thank You, Gord
  14. gordonl

    Pulling Cable in Trench

    Could anyone share info on the coefficient of friction for pulling PVC jacketed cable on sand. I've had no success with the resources available to myself. Thank You, Gord
  15. gordonl

    Cable Shield Type

    I'm ordering some 35 & 15kV cable, and I've gnerally required wire shield in the past to acheive the required current and time rating for clearing ground faults on my system. A manufacture has proposed a "heavy" tape shield this time around, which meets the above requirement. Does...
  16. gordonl

    Eddy Current

    Can anyone give me a rough method of calculating eddy current losses? Here's the situation: I have a high current conductor (10kA-20kA) bolted to a chunk of stainless which is enventually insulated. How can I make a rough estimate for eddy current losses in the stainless? The stainless is 304...
  17. gordonl

    Transformer Winding Costruction

    A transformer designer has suggested to me that a disc winding is mechanically superior to a sheet (foil) winding. Any comments thoughts? In reference, we experienced a 13MVA rectifier transformer failure, apparently due to failure of the low voltage due to mechanical stress between layers...
  18. gordonl

    Ground vs. Neutral

    I have electronic relays with three phase CT's connected in wye after the phase inputs, and run through the ground element of the relay. The system is 3 wire, resistively grounded to 1000A. Anybody see any advantage/disadvantage to using ground settings on the relay versus neutral settings for...
  19. gordonl

    MV Metalclad Bus Differential

    I'm in the process of replacing an old 15kV metalclad lineup and am wondering what others are using for bus protection. In the past we've used graded overcurrents which gave delays of upto several seconds for solid bus faults. I'm currently looking at blocking & tripping of instantaneous...
  20. gordonl

    Rectifier Transformer

    I'm in the process of purchasing a spare rectifier transformer and would appreciate any input for my bid spec. Any recomendations on winding design, ie sheet, disc, etc. Could anyone supply an old spec which I could review. The transformer will supply a cycloconverter at 1150V for a 9200kW...

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