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Thread: Power Technology

  1. #1 Power Technology 
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    Unheard of not too long ago, today solid-state devices, traditionally known to operate on lower voltage levels than the mainstream everyday electrical devices, now have been developed with capability of use in High-Voltage Power Transmission.

    HIGH-VOLTAGE THYRISTORS

    The article points out that 84,000 Thyristors, these being semiconductor devices like transistors, would only recently have been needed to operate a 3000 megawatt facility; today's components can do it with only 3800 of them! Talk about break-throughs? For some reason, my link lacked info beyond what I've said here. Important point is that YESTERDAY'S technology needed to convert D.C. to A.C. was wasteful, cumbersome, MECHANICAL, and limited in voltage level, today the "sky's the limit". As a student/worker/user of yesterday's stuff, this blows me away! Today, we can harness "lightning bolts" using solid-state components (basically!).

    Scientific advancement moves ahead, despite the "negatories" experienced in the forum! jocular


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    What is nuclear power technology?


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  4. #3  
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    Quote Originally Posted by HeartBreaker View Post
    What is nuclear power technology?
    Please re-phrase your question. An answer to it as stated would entail printing out a book. jocular
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    I once stuck a thyristor into a final amp circuit on a CB. Final amps usually have a gain factor like 10 or 20. The thyristor had a gain factor of about 1. The circuit worked about as well as using two diodes back to back. The thing worked ok. Now I was wondering ,a solid state rectifier being a diode on a heat sink, what if you hooked two of them back to back for power control. Or for even more power a parallel group of the things. Gone are the good old days of the CB but I still have the Ham.
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  6. #5  
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    Quote Originally Posted by Hill Billy Holmes View Post
    I once stuck a thyristor into a final amp circuit on a CB. Final amps usually have a gain factor like 10 or 20. The thyristor had a gain factor of about 1.
    Thyristors won't self-commutate so they generally don't work as linear amps. Not surprising that you didn't see any gain.
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    OK, guys! No commitment, so tell me how in the fu`k are they effectively transmitting 500,000 volts DC from Hoover Dam to Phoenix, about 200 miles, and turning it back into A.C. at the use point? Any idea what power is transmitted? Thus, what is current level in the lines? What about ENORMOUS static potential built up along those lines, non-existent using A.C. Are D.C. lines more amenable to lightning strike? The whole frigging line 200 miles long is a GIGANTIC charged capacitor, the conductors comprising the "plates", no? In the event of a "fault", momentary shut-down due to perhaps a big lightning strike (grounded out), where does the stored energy in this god-awful huge field go, as it collapses?

    If it were up to you, would you transmit D.C. using 2 conductors, or maybe use 4, keeping conductor locations appropriately spaced to avoid load-variation induced effects from one affecting the other?

    Do you think D.C. power transmission is "God's gift? jocular
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    this may be of interest jocular

    Basslink - Wikipedia, the free encyclopedia
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    Sometimes it is better not knowing than having an answer that may be wrong.
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  10. #9  
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    Quote Originally Posted by Chrispen Evan View Post
    this may be of interest jocular

    Basslink - Wikipedia, the free encyclopedia
    Holy Shit! Thank you for this! A SUBMERGED half-million volt line carrying D.C. power! Unimaginable in my earlier days, still so today! What sort of insulation can withstand the corona discharge at such high-voltage, which produces materials-devastating ozone, in the open air, but I wonder about underwater? May be even worse, seawater highly conductive.

    Good Grief! Please excuse my "French"! I'm flabbergasted! jocular
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  11. #10  
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    Thank you, also! The following excerpt is open to question:

    "One major advantage of High-voltage direct current over AC is that the DC current penetrates the entire conductor as opposed to AC current which only penetrates the so called skin depth, which is inversely proportional to the square root of the frequency. Even for a frequency as low as 60 Hz the skin depth is less than the 1.6" radius of the conductor used for the Intertie. Hence the effective resistance is greater with AC than DC, so that more power is lost to heat. A DC line is also ideal for connecting together two AC systems that are not synchronized with each other. Also, cascading blackouts are less likely."

    This is like saying no current flows at the center of a conductor; I do not believe that is quite true, but it's not terribly important. The conductors used on High Voltage A.C. transmission lines are typically hollow tubing made of narrow strip-like segments interlocked together along their length, with a slight twist thrown in. Short pieces of this stuff were for sale at the Hoover Dam Visitors Center years back; they may still be available. As I recall, the outside diameter was a bit over 1", the inside about 3/4".

    "the effective resistance is greater with AC than DC, so that more power is lost to heat"

    "Effective resistance" is impedance, certainly an unwanted factor in A.C. transmission, but I fail to understand the sentence as worded: heating effect is a function of current intensity and resistance only. So the author's intent escapes me.

    The following:

    "However, if direct current is used, the cable capacitance is charged only when the cable is first energized or if the voltage level changes; there is no additional current required. For a long AC powered undersea cable, the entire current-carrying ability of the conductor would be needed to supply the charging current alone. This cable capacitance issue limits the length and power carrying ability of AC powered cables. DC powered cables are only limited by their temperature rise and Ohm's Law. Although some leakage current flows through the dielectric insulator, this is small compared to the cable's rated current."

    Also deserves consideration. In order for no capacitive loss to occur using D.C., the voltage must remain constant. From a consideration of actual operating experience, I wonder just how constant can voltage level be held, given the large load variations which may be expected. jocular
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