Search:

Type: Posts; User: ggunn

Page 1 of 8 1 2 3 4

Search: Search took 0.28 seconds.

  1. Replies
    26$$
    Views
    569

    I get that; I studied transmission lines in...

    I get that; I studied transmission lines in school, back when dinosaurs walked the earth. What I am looking for is a definition of what it is and where the 75 ohm number (or whatever) is measured or...
  2. Replies
    71$$
    Views
    1,293

    So, are we back to a choice between installing a...

    So, are we back to a choice between installing a delta to wye isolating transformer for the entire load with a grounded neutral (separately derived) or pulling a neutral from the service?

    The...
  3. Replies
    71$$
    Views
    1,293

    OK, assuming that he can derive a neutral with an...

    OK, assuming that he can derive a neutral with an autotransformer between the A and C phases and connect it to the machine in question, what sort of current handling capacity will it need to have to...
  4. Thread: Medium voltage

    by ggunn
    Replies
    12$$
    Views
    289

    Thanks; that is what I have been doing. I am also...

    Thanks; that is what I have been doing. I am also going to talk to someone at the electricians' union to see if they have any suggestions.
  5. Replies
    71$$
    Views
    1,293

    If he did that would the neutral thus generated...

    If he did that would the neutral thus generated be at equal potential with earth ground at the machine? Would he (could he) bond the neutral to ground at the panel? It seems potentially (no pun...
  6. Thread: Medium voltage

    by ggunn
    Replies
    12$$
    Views
    289

    Last year I worked on a response to an RFP for a...

    Last year I worked on a response to an RFP for a multi MW PV system at an airport. The interconnection point was to be a backfed breaker in a massive medium voltage MDP. That kind of interconnection...
  7. Replies
    71$$
    Views
    1,293

    If the machine requires a 4W service and...

    If the machine requires a 4W service and internally runs its control circuitry off one of the non-high legs and ground, it seems to me that his choices are pretty much down to either installing a...
  8. Replies
    71$$
    Views
    1,293

    A quite possibly stup... I mean, ignorant...

    A quite possibly stup... I mean, ignorant question which very well may have already been addressed: Why couldn't the OP place a 1:1 three phase transformer with a center tap between A and C phases...
  9. Thread: Medium voltage

    by ggunn
    Replies
    12$$
    Views
    289

    Exactamundo. If all you have to do is land your...

    Exactamundo. If all you have to do is land your 480V (or whatever) on the LV side of an existing transformer to MV then it's no biggie. If you have to design the MV circuit itself then it's a...
  10. Replies
    23$$
    Views
    362

    Then as an engineer you revert to a Scottish...

    Then as an engineer you revert to a Scottish brogue and say, "I cannae rewrite the laws of physics, Cap'n! She's gonna blow!" :D
  11. Thread: Medium voltage

    by ggunn
    Replies
    12$$
    Views
    289

    Those are the fundamentals, yes, but the devil is...

    Those are the fundamentals, yes, but the devil is in the details.
  12. Replies
    26$$
    Views
    569

    For my education, can you give me a quick...

    For my education, can you give me a quick explanation of what the characteristic impedance of a type of cable is a measurement of? Is it an impedance/resistance per some unit length, and is it...
  13. Replies
    23$$
    Views
    362

    Got it, but I would think that showing an...

    Got it, but I would think that showing an inspector the specific proscription by the NEC of backfeeding any breakers with line/load designations would be enough.
  14. Thread: Medium voltage

    by ggunn
    Replies
    12$$
    Views
    289

    Thanks for the link. I found them yesterday; I...

    Thanks for the link. I found them yesterday; I plan to talk to them, but the wording on that page implies to me that having them build a custom course for me would be expensive. Perhaps prohibitively...
  15. Thread: Medium voltage

    by ggunn
    Replies
    12$$
    Views
    289

    Medium voltage

    Have any of you guys ever designed PV systems that interconnected at medium voltage? If so, where did you pick up the skills necessary to accomplish that? I have looked for training that would apply...
  16. Replies
    23$$
    Views
    362

    I figured you did. Why is it an issue, since...

    I figured you did. Why is it an issue, since backfeeding a line/load marked breaker is forbidden by the NEC? That's my polite way of saying "Who cares?" :D
  17. Replies
    23$$
    Views
    362

    I don't know what would happen, physically, but...

    I don't know what would happen, physically, but the NEC says you cannot backfeed a breaker that is marked line and load.
  18. Replies
    71$$
    Views
    1,293

    Stupid response deleted.

    Stupid response deleted.
  19. Replies
    71$$
    Views
    1,293

    There is a neutral at the transformer and/or main...

    There is a neutral at the transformer and/or main panel, just not at this panel 400 feet away. He is trying to avoid having to pull a neutral 400 feet through an occupied conduit. I don't blame him.
  20. Replies
    71$$
    Views
    1,293

    He said that the 4th wire was ground.

    He said that the 4th wire was ground.
  21. Replies
    71$$
    Views
    1,293

    Never mind, after typing a rather longwinded...

    Never mind, after typing a rather longwinded response I realized that I was simply restating the obvious.
  22. Replies
    10$$
    Views
    359

    <deleted>
  23. Replies
    10$$
    Views
    359

    One thing to consider is that if your inverter...

    One thing to consider is that if your inverter requires a 35A breaker but you use a 40A breaker instead, you will probably have to size up your conductors. Your conductors must be protected by the...
  24. Replies
    12$$
    Views
    580

    You are correct that it is not a material...

    You are correct that it is not a material property per se, though it's not exactly a surface effect, either. The thickness or depth of the film or implant is a factor, as is the dopant concentration...
  25. Replies
    6$$
    Views
    367

    It could be a great option, or not. You have to...

    It could be a great option, or not. You have to do the math and see how it works for you.

    If you lease a system, then the owner of the system (Solar City, in this case) gets some of the economic...
Results 1 to 25 of 200
Page 1 of 8 1 2 3 4