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  1. BigMotorGuy

    690v 3 phase application lead wire rating

    Stupid question, but I have an application going into a 690v 3 phase system, so since the actual voltage to ground on any of the 3 legs is 690/sqrt3 = 398.4v using 600v rate wire is ok right?
  2. BigMotorGuy

    NEC 500 Class I/Div I Purged Junction Box Requirements

    We run a test stand that is rated Class I/Div I hazardous area in which we run multiple electric pumps from low voltage up to 6600v. Since we install and tear down the pump connection setup on a daily basis (hence the test stand designation), we do not have the luxury of having sealed AEx e...
  3. BigMotorGuy

    R134a Refrigerant Corrosion

    Looking for material compatibility of typical induction motor components when exposed/submerged in R134a refrigerant, specifically ixlpe lead wire insulation and epoxy resins.
  4. BigMotorGuy

    Junction Box Ratings versus minimum wire size?

    I have a given junction box that has a current rating above the rating of the load (induction motor). The box stated a minimum wire size which ties into the box current rating. Since the load is much lower than the box rating (e.g. 250 amp box rating for a 100 amp FLA motor rating), do I still...
  5. BigMotorGuy

    Easiest way to provide constant 250 ARMS for junction box thermal testing?

    I am looking for the best/easiest way to perform a temperature rise test (i.e. measure box temperature with 250amps flowing through the 3 phases - need a T6 rating) on a new junction box which is rated at 6.6kv and 250amps. Will simply finding a constant current power supply rated to 250amps or...
  6. BigMotorGuy

    Phase Rotation Check - 3.3kv Submerged Generator

    I have a need to verify phase rotation on a submerged expander generator. We are in testing phase and need to verify the correct rotation prior to trying to synch with the power grid. This is a 2MW induction generator (2 pole) and we do not have access to the unit as it is submerged in LNG...
  7. BigMotorGuy

    IEC 61000-6-4 EMC Testing for 3 Phase Induction Motors?

    Do 3 phase squirrel cage induction motors (550Hp, 3.3kv, 50Hz) produce EMI which may be problematic for IEC 61000-6-4? Do different neutral grounding systems (i.e. ungrounded, grounded, resistance grounded, etc.) have any affect on this? I believe this standard references a frequency range...
  8. BigMotorGuy

    Induction Motor or Generator EMC/EMI Testing?

    Do DOL induction machines in general generate EMI levels which need to be considered? Does NEMA or IEEE address induction machines in regard to electrical noise? I realize that if they are VFD driven, this can be an issue due to the drive itself, but wondering if DOL applications need to be...
  9. BigMotorGuy

    Synchronous Reactance for Induction Motors?

    Is the synchronous reactance a parameter for asynchronous induction motors or does it only apply to synchronous machines? If so, how does one calculate it from typical equivalent circuit info? Also, how does one determine the transient time constant on an induction motor in the event of a...
  10. BigMotorGuy

    Epoxy VPI System Vacuum Levels

    In regard to form wound induction motors, are there any drawbacks to drawing a higher than recommended vacuum(recommended by the VPI equipment manufacturer)? For example a recommended vacuum level of 3 torr is typical for using epoxy resin. Is going to less than 1 Torr going to cause any...
  11. BigMotorGuy

    PI Test Values AC Induction Motors: Random Wound Versus Form Wound Ratios

    I work at an induction motor manufacturer and we routinely do PI tests on newly constructed 3 phase stators. All the info I have read on PI ratios says anything below 2 is suspect. However, we routinely test smaller (e.g. 10Hp, 380v 2 pole) random wound stators measure very near 1. It...
  12. BigMotorGuy

    Estimating Starting Current in 3 Phase Induction Motor by Single Phasing

    Can you accurately estimate the starting current in a 3 phase induction motor by applying single phase power to the motor while stopped, measure the current and then multiply this single phase current by a factor? What factor do you multiply the single phase current by to get the total 3 phase...
  13. BigMotorGuy

    IEC Electrical Testing for Random Wound Stators?

    Are there any specific IEC electrical tests standards which apply directly to random wound stators which are different than NEMA/IEEE standards? I know there are specifics for form wound stators which differ from NEMA/IEEE tests (i.e. impulse tests on a set of sacrificial coils as well as on...
  14. BigMotorGuy

    Liquid cooling flow rates for proper cooling of an induction motor

    I need to determine the minimum flow rate of liquid required to cool a random wound 3 phase induction motor (150Hp, 575v). This will be a submerged pump which will divert a +40C fluid through the motor housing along with through the air gap. How can I relate the required flow per motor watt...
  15. BigMotorGuy

    Baker Explorer Torque Measurements

    To All, Does anyone have a good understanding of the torque readings measured using Baker's explorer test units and how they actually compare to dyno test torque values for induction motors? I deal with submerged pump motors (50Hp thru 3500Hp, 480 thru 6.6kv) that are integral to the pumps...
  16. BigMotorGuy

    Fault Withstand Ratings

    The concept of fault withstand ratings for a pump motor and associated power supply equipment was requested by a customer. I understand that junction boxes, feedthrough terminals, and power cabling needs to have a fault withstand rating, but does a motor need to have this rating? Since the...
  17. BigMotorGuy

    Squirrel Cage Rotor Production Testing

    Does anyone have any experience with squirrel cage rotor test systems beyound the standard growler test? We currently purchase various rotors (10Hp thru 3000Hp, 2,4, and 6 pole applications) and currently only do a traditional growler test prior to motor build. We have seen suspect failed...
  18. BigMotorGuy

    Stacking Factor versus compression force

    It is my understanding that the resultant stacking factor for an induction motor core is due to the lamination insulation layer but also the amount of compression on the core prior to welding/fastening. What is the best way to determine the compression force needed to obtain the maximum SF...
  19. BigMotorGuy

    NEMA MG-1 2009 Insulation Resistance Values

    It is my understanding that the minimum acceptable insulation resistance values have been updated in the 2009 MG-1 standard.....does anyone know what the new values are? Are they different from the IEEE 43 values?
  20. BigMotorGuy

    IEC 60851 versus NEMA magnet wire specs

    Does anyone know the differences in magnet wire and its related testing between IEC 60851 and NEMA rate wire? We typcially use double Daglass coated HAPTZ style magnet wire, but a customer is asking for IEC 60851 rated wire. any notes on what all IEC 60851 covers would be appreciated.

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