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  • Users: coolfish
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  1. coolfish

    Reactive Capability Curve

    Thanks again. What we are trying to do is to monitor the operation of our generator relative to its capability curve. If the operating point is within the curve, nothing further is required. If the operating point is outside the curve, the difference is recorded as well as the time it operated...
  2. coolfish

    Reactive Capability Curve

    Thank you very much for the information. Is the Siemens/Westinghouse paper, Adjustment of Generator Capability Curve available? I've checked their websites and did a search but I can't find any reference to the article/paper.
  3. coolfish

    Reactive Capability Curve

    Does anyone know how to draw a generator reactive capability curve as a function of the cooling air (for an air cooled machine)? The centers of the circles are fixed but the radii of the circles will vary as a function of temperature (assuming constant voltage and frequency). Both stator and...
  4. coolfish

    Safety agnecy approvals

    Is is true that there is a 'Special Inspection' program accepted by the Authority Having Jurisdiction (which is not necessarily the Province or municipality). However, there are very few equipment where there no standards. While there is no such thing as an approved liquid-filled transformer...
  5. coolfish

    Safety agnecy approvals

    In Alberta, it is illegal to sell or use electrical equipment are not approved by any of the approved certification agencies certified by the Standards Council of Canada. This is clearly stated in the Canadian Electrical Code and the Electrical Regulation. (I am sure other Provinces have similar...
  6. coolfish

    normal current imbalance levels

    Motor heating (stator and rotor) is caused by the I2T heating of both positive and negative sequence currents. This heating is compared with the manufacturer's thermal damage curves. So, as a general statement, even if the motor is not fully loaded, it is possible to damage the motor depending...
  7. coolfish

    Motor Space Heater Sizing Thumbrule

    The temperature should be above the dew point, not just above the ambient.
  8. coolfish

    Table 124 of ANSI C2, National Electrical Safety Code

    I got a 1997 edition of the NESC. If that is good enough, I'll scan and e-mail or fax it. Table 124 is Clearance from Live Parts.
  9. coolfish

    CSA standards

    What you are referring to as E standards are standards for equipment for classified areas. Remember, Canada has adopted the zone system for class I locations instead of the divisions (NFPA). Those 'E' standards are based on IEC standards and they are some changes. As far as I know, these are not...
  10. coolfish

    Standards on providing motor differential CT's ?

    I believe it is optional. NEMA standards do not require them, especially for 250Hp, which is is still 'small'. Even RTDs are not required, especially bearing RTDs.
  11. coolfish

    overload relays

    I would say that good practice is to hardwire the N/C contact in series with coil. If your O/l has an available NO contact, you can still connect this to a PLC input. You can then also trip the motor via logic in addition to the hardwire NC contact.
  12. coolfish

    Battery life for emergency lighting

    Depends on the type of battery. Some batteries, although may have a listed life of 10 years, may fail in 3. Most would require replacement in no more than 7. Only a few will actually last 10 years or more. Or course, this also depends on the number of discharge and charge cycle, temperature...
  13. coolfish

    FAILURE OF MOTOR BY FLASHOVER IN STATOR

    Could be referring to partial discharges (sparks) which could be mistaken for 'flashover'. Not aware of a protective device that will protect from such discharges. Generally protective devices will respond to other failures like grounds. But the partial discharges can be measured off line or...
  14. coolfish

    How far can you adjust the Power Factor on a Synchronous Motor?

    V-curves and capability curve will help in analyzing the performance of the machine. If the machine reactances are knowb, you could draw the capabilty curve.
  15. coolfish

    Anybody know who took over the West

    If not ABB, try Siemens.
  16. coolfish

    600V Generator for 480V System

    It might work but probably not recommened. Why not use a step down transformer instead, either three winding or auto-transformer? Of course, you will have to wire a 1.5 MVA transformer which could be substantial in size.

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