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  1. rhatcher

    interrupt current

    The primary factors are - transformer voltage and kVA - conductor size and distance to the panel - possibly load contibution downstream The basic answer can be had from a table. A more precise answer is obtained by a calculation method. Several other threads in this forum have contributions on...
  2. rhatcher

    3 phase power generation

    To answer arc480, once you establish that the phase rotation is the same, the act of synchronizing the generators ensures that the phase sequence is correct. I agree with electricpete that these terms are often interchanged. However, on a fine point the terms may not be synonymous. As an...
  3. rhatcher

    Single Phase AC Motors

    Once again electricpete and peterb nailed this one down. Stars for pete and pete...
  4. rhatcher

    Measuring power off a ATX power supply

    I have never tried to do what you are trying to do before, but based on common sense I assume the one ohm resistors were to be used as a DC current shunt to measure current flow by voltage drop. Resistors are cheap so you may select a smaller value, say 0.1 or 0.01 ohms. I would pick the...
  5. rhatcher

    step up, step down transformer requirements

    Chris1957, First, I will say that what follows is meant in a helpful way as my advice to you and should not be construed as anything else... You should probably get a copy of the NEC or whatever standard is applicable for your installation and location and familiarize yourself with the...
  6. rhatcher

    step up, step down transformer requirements

    Please clarify the following: - For the 208V 60A service, what it the method of installation for the conductors (ie, in conduit, raceway, buried....? - For the 5 locations at 1300ft, a) method of installation as described above? b) distance between the five locations...if they are...
  7. rhatcher

    U.K to U.S.A 3 phase

    I do not have an answer for the voltage conversion question but am curious as to whether your equipment is frequency specific as I understand that the UK is 50hz and the US is 60hz.
  8. rhatcher

    Under voltage relay setting

    There are several parameters to consider for undervoltage relay settings. There is no fixed standard value to use for either time delay or dropout voltage. The combination of the settings you choose must be based on your situation. Unfortunately, if you are using a simple relay having a fixed...
  9. rhatcher

    Testing breakers

    jbartos's recommended pub GEC-7002C is available on the web. You should definitely become familiar with it if you plan to do anything more than turn on one of these breakers: http://www.geindustrial.com/industrialsystems/circuitbreakers/applicat/cb-pd-et/index.htm Select pub# GEC-7002C. Page...
  10. rhatcher

    Testing breakers

    Excellent post peterb (complete and concise). If specific information is needed on time-current curves or acceptable values of contact resistance please respond with the breaker nameplate information (ie. manufaturer, model number, current rating, etc.)
  11. rhatcher

    CAPACITOR CURRENT FORMULA

    First: jbartos says ... Suggestion: Consult Reference 1. NFPA 70-1999 Article 460 - "Capacitors" 460-2A(b) "Means of Discharge" since there shall be discharge circuits..... Remark: The discharge circuits will add some smaller current to the line...
  12. rhatcher

    Is there anything out there to read

    The NEC will provide tables for current carrying capacity of wires based on standard ratings. The wire will be rated according to type (solid or stranded, Al or Cu, etc.), diameter (in AWG or CM), by insulation type and insulation temp rating, and installation method (open air, conduit, etc). I...
  13. rhatcher

    CAPACITOR CURRENT FORMULA

    Thank you peterb! That is the correct answer. As has been the case before in this thread, it was followed with a response that was meaningless...
  14. rhatcher

    CAPACITOR CURRENT FORMULA

    For jbartos: In reviewing your "supplement" to my terminology, I agree that the terms you provided for the wye case are somewhat synonymous, but I don't agree with all of the terms in the delta case. Either way, I am not familiar with the fact that the reference you cited (STD 242)...
  15. rhatcher

    CAPACITOR CURRENT FORMULA

    More recent references only appear to support my orginal points. 1. With respect to your referenced definition: phase voltage of a winding (machine or apparatus): "The potential difference across one phase of the machine or apparatus". That reference supports my definition as...
  16. rhatcher

    CAPACITOR CURRENT FORMULA

    First, to answer RDTDIRECT's question regarding installation of a capacitor bank, the current to be supplied to the bank from your power source (ie. switchgear)will be 240A at 480V. Conductors and overcurrent protection should be sized as such based on NEC recommendations. With respect to...
  17. rhatcher

    CAPACITOR CURRENT FORMULA

    line current = current between source and load phase current = current in a phase (leg) of source or load wye connected: line current = phase current delta connected: line current = sqrt3*phase current The line current for your bank will be 240 amps at 480V regardless of the type of connection...

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