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  • Users: ePOWEReng
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  1. ePOWEReng

    Matrix math with complex numbers

    Hello, I am considering taking some calculations that presently performed using MathCAD and creating an application to perform those calculations instead. The calculations involve creating a matrix of complex numbers and performing some matrix math operations to arrive at the solution. The...
  2. ePOWEReng

    Matrix math -- Application development

    Hello, I am considering taking some calculations that presently performed using MathCAD and creating an application to perform those calculations instead. The calculations involve creating a matrix of complex numbers and performing some matrix math operations to arrive at the solution. The...
  3. ePOWEReng

    1 phase with unequal impedance

    There are some single phase banks transformer banks in our system which have back up transformers with different impedances. It could happen that if a certain transformer failed a backup may be used which has an impedance 10% different from the remaining 2. Has anyone ran into this...
  4. ePOWEReng

    change Wound rotor motor to VFD fed induction motor

    There are existing 1600HP wound rotor motors driving centrifugal pumps at a water pumping station. There is a push to convert the motor to a VFD driven induction motor. The VFD cost is high. The thought is that reliability would be improved. Also maintenance on the slip rings would go away...
  5. ePOWEReng

    add bracing to existing LV MCC

    Does anyone have experience increasing the rating of an existing 480V MCC via installing additional bracing for on the bus (e.g. 45kA rms to 65 kA rms)? Is this a via alternative to installing a new MCC? Any technical papers on this subject? Thanks for your responses!
  6. ePOWEReng

    new MV drive on old motors

    I am working on a project installing a Medium Voltage drive an old induction motor (4160V, 2000HP). I am interested in hearing peoples thoughts on the different drive technologies and manufactures out there. For instance, ABB offers a standard PWM inverter at 4160V, 2000HP with an sine wave...
  7. ePOWEReng

    RPM sensor motor connected to VFD

    When is a RPM sensor needed on a motor that is connected to a VFD? VFDs can estimate the RPMs of a motor but when is this not accurate enough? Thanks!!
  8. ePOWEReng

    StormWater Wet Wells NFPA 70 (NEC) Classification

    Does anybody know what codes are applicable for NEC classifications of stormwater wet wells? Are there any Class 1 division 2 areas in or around the wet wells? Thanks!
  9. ePOWEReng

    Industrial Ground Methods

    Hello. I am trying to get information on what type of grounding methods are typically used in industrial facilities. I realize this is going to vary with the type of industry, but just trying to get a general feel. Also what type of protection elements are being used for SLG fault detection...
  10. ePOWEReng

    Transmission Line and cable parameter program

    Hello. Does anyone know of a free transmission line and cable parameter program that is avaliable for excel, or can be run through a website, or possibly a stand-alone freeware program? I have a bunch of mathCAD worksheets but sometimes I have a hard time getting use a machines that have...
  11. ePOWEReng

    NEC Hazardous Area Classification

    I am an employee of a company that designs, builds, and performs testing on large LPG/LNG pumps. I am trying to classify the hazarous areas around the test stand, the storage tanks and the transfer area, but am having trouble finding solid references. The NEC says in reference to Class I...
  12. ePOWEReng

    Voltage Insulation Level UG Cable

    Hello. What is the proper voltage insulation level for a NEC application running a 6.6kV motor? Using the utility theory, you go by the line-line voltage so we would probably need to buy 15kV cable. Right? But do the same criteria apply to a single 3-phase UG feed to a pump? Does the...
  13. ePOWEReng

    what to do with used 1500 kVA m/g set?????

    Hello. I have a 1500kVA m/g set that I am looking to sell. The Unit was built in 1984. The DC motor works perfectly and is in good shape. The AC generator has a bad stator winding but otherwise is in good shape. The run time is very low. Anybody know how or where the best place to get rid...
  14. ePOWEReng

    75 ohm cable with 50 ohm BNC connectors

    I am wondering if there is a large impact with using a 50 ohm BNC with a 75 ohm cable. We are using this with about a 50kHz signal. Is the dB drop going to be anything to worry about??? Thanks in advance for your help.
  15. ePOWEReng

    Leads of a three phase induction wye-wye motor

    Hello. Does anybody know how to find the correct 'pairs' of leads for a induction motor that is connected in a double wye configuration with the two wyes completely electrically disconnected. The two 'wye points' are not accessible, only the six phase leads. We are able to use an ohm meter to...
  16. ePOWEReng

    Resistance Model of Two-Winding Transformer

    Hello! I am working for a utility modeling the two winding substation transformers (generally 115kV Delta-13.8kV Wye-ground on our system). We have test reports for all of these transformers and in the past we have used the resistance from the test report in our transform models. It has been...
  17. ePOWEReng

    Underground Transformers

    Does anyone have experience or knowledge about residential underground direct buried distribution transformers and/or residential distribution transformers in an underground vault? What are reasons that you use or do not use them? Thanks.
  18. ePOWEReng

    UG fault indicators

    Does anybody have experience with applying Power Delivery Products self-adjusting current trip fault indicators on a industrial UG feed such as a hospital? Or any other type of UG circuit for that matter. I am thinking about using them on a UG circuit, but wonder about there accuracy and...
  19. ePOWEReng

    1-phase voltage regulators and distribution switching

    Does anybody know whether or not voltage regulators will "hunt" (that is due to circulating current which increasing with the tap change, one goes to max boost and the other to max buck) when paralleled (parallel connections are on in the 13kV distribution system and one in the 115kV system), if...
  20. ePOWEReng

    QF interconnection

    does anybody know what ANSI/IEEE standards talk about interconnection to a Qualifying Facility?

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