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Type: Posts; User: synchro

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  1. Replies
    6$$
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    Do any of the cell modem and cloud-based...

    Do any of the cell modem and cloud-based monitoring solutions for the photovoltaic market include near real time alarms if programmed limits have been exceeded?
    I know this capability is offered for...
  2. Thread: VFD's Tripping

    by synchro
    Replies
    17$$
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    605

    Yes, the current through a series inductor is the...

    Yes, the current through a series inductor is the integral of the voltage across it (plus a constant) and so it will slow down the rate of rise (and the rate of fall) of the current. Of course if you...
  3. And if conductors have to be pulled because old...

    And if conductors have to be pulled because old ones have failed, then the liklihood that conduits have shifted or been crushed, etc. is even higher.
    If there are existing wires have you checked...
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    12$$
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    414

    Wayne beat me to it ;)

    Wayne beat me to it ;)
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    12$$
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    414

    One possibility could be to dig down somewhere in...

    One possibility could be to dig down somewhere in the middle of the run that would have a 465 degree cumulative angle after your 45 and 90 elbows are added in. Then you could cut the conduit, attach...
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    2$$
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    175

    I agree that the annex shows the proper way to do...

    I agree that the annex shows the proper way to do the demand calculation. I believe the intent of the wording "shall be calculated on the basis of" does not mean that the kW from the table is the...
  7. Thread: VFD's Tripping

    by synchro
    Replies
    17$$
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    605

    IGBTs are also subject to latch up because of...

    IGBTs are also subject to latch up because of their NPNP structure like in an SCR (which I like to think of as an NPN and a PNP connected with positive feedback):
    ...
  8. Thread: AB140m

    by synchro
    Replies
    24$$
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    982

    Those readers and tags are on the LF (low...

    Those readers and tags are on the LF (low frequency) RFID band with carrier and modulation sidebands in the vicinity of 130 to 140KHz. So filtering of the VFD output to get sufficient attenuation at...
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    Yes, VDC = 3sqrt(2)/pi x VLine-Line RMS = ~1.35...

    Yes, VDC = 3sqrt(2)/pi x VLine-Line RMS = ~1.35 VLine-Line RMS

    About 1.4VDC should also be subtracted from the output to account for voltage drops in a pair of diodes inside the bridge.



    ...
  10. Replies
    5$$
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    482

    The following is a comment from EasyPower about...

    The following is a comment from EasyPower about rectifier fault current:

    "Diode rectifiers can have DC terminal fault current close to the AC side fault current."
    ...
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    5$$
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    482

    Do the rectifiers have any filter capacitors...

    Do the rectifiers have any filter capacitors associated with them?
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    I'm late to the game on this thread but I agree...

    I'm late to the game on this thread but I agree with this comment.
    I also don't think there's a good engineering justification to reduce the requirement on the busbar current rating by...
  13. Thread: 2phase 4wire

    by synchro
    Replies
    27$$
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    1,336

    Some other 4-pole 100A safety switches: Square...

    Some other 4-pole 100A safety switches:

    Square D 600V rating...
  14. Thread: 2phase 4wire

    by synchro
    Replies
    27$$
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    1,336

    I see that Philadelphia PECO supplies 2-phase...

    I see that Philadelphia PECO supplies 2-phase 5-wire 120/240V. So basically the distribution transformers use two center-tapped windings driven at 90 degrees from eachother, with a common neutral...
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    12$$
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    509

    There is a Department of Energy mandate to...

    There is a Department of Energy mandate to improve the efficiency of fan motors, so that might be what it's about:
    ...
  16. It appears that capacitor start motors were first...

    It appears that capacitor start motors were first developed around 1925:

    http://ece.umich.edu/bicentennial/chairs/bailey.html

    They were quickly applied in refrigerators because of their high...
  17. That behavior sounds more like a capacitor where...

    That behavior sounds more like a capacitor where the current will decrease as the cap voltage gets closer to the thevenin equivalent source voltage of the ohmmeter itself, because I=CdV/dt. The...
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    15$$
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    910

    I think if those conductors are not bundled...

    I think if those conductors are not bundled together for more than 24 inches, then derating is not required. But I could be wrong about that.

    310.15(B)(3)(a)(2).
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    15$$
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    910

    Could the existing wiring be brought into a...

    Could the existing wiring be brought into a 4×4x24" 3R wiring trough that's surface mounted, and then connected with conduits to a 3R panel surface mounted below it? Obviously any gaps left would...
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    51$$
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    2,781

    The following link does a good job covering this...

    The following link does a good job covering this issue:
    ...
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    15$$
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    852

    Of course, double check that the delta secondary...

    Of course, double check that the delta secondary has not been corner grounded. If it was then any bonding to ground on that line would need to be removed, and overcurrent protection added on the...
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    6$$
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    522

    I also suspect the night sensing light could be...

    I also suspect the night sensing light could be causing the AFCI breaker to trip. When the light is just on the threshold of switching near sunset it may be creating noise on the branch circuit which...
  23. Replies
    51$$
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    2,781

    More detailed modeling info for distribution...

    More detailed modeling info for distribution transformers with center-tapped outputs under both normal loading and short circuit conditions is presented in the following paper:
    ...
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    5$$
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    542

    Do you know that it actually uses all 3 phases? ...

    Do you know that it actually uses all 3 phases?

    Most DC supplies nowadays rectify the AC input with diodes and then use a higher frequency switching supply because any transformers, capacitors,...
  25. Replies
    51$$
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    2,781

    I think the %Z is higher with the 120V winding...

    I think the %Z is higher with the 120V winding than the 240V full winding because there is more leakage flux that does not couple to both the primary and secondary when using just the 120V half...
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