Glen Herrmannsfeldt wrote:> The question is, what would be the advantages and disadvantages > to switching to 20kHz power from 60Hz?All losses will be greater by orders of magnitude. Skin effect, capacitive/inductive spillage, losses in the core, switching losses, rectifier losses, etc.> How much more efficient are ferrite transformers at 20kHz than > our usual silicon steel power line transformers?It depends. There is no fundamental difference.> Assuming > one uses superconducting DC power lines, how much easier is it > to convert from DC to 20kHz? How much more efficient are various > SCR based power controllers at 20kHz?SCRs won't work at 20kHz. The valid switching elements for that frequency are FETs, and, may be, IGBTs.> How much would 20kHz to 60Hz > converters cost?A lot :)> Most likely not practical, but there will have to be big > changes in energy use in the coming years to reduce the > global warming contributions. More efficient use of electrical > power would help.What could make sense is switching to the DC power, like they did in the modern aircrafts. The problem is the electrolitic effects destroying the wiring. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
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Duality in continous Fourier transform
Started by ●October 28, 2008
Reply by ●October 30, 20082008-10-30
Reply by ●October 30, 20082008-10-30
Glen Herrmannsfeldt wrote:> Jerry Avins wrote: > > (snip on 20kHz power distribution) > >> The biggest problem would be in distribution. Radiation would become >> much more of a problem, and dielectric losses would overwhelm the >> energy budget. Even with 60 (or 50) Hz, transmission losses are high >> enough to provide a strong incentive for high-voltage DC transmission. >> Power is generated at AC, then stepped up to 400 KV and rectified. >> Semiconductor devices convert back to AC at the receiving end. The >> inevitable losses and the cost of the equipment are amply repaid by >> the savings. > > Isn't it easier to convert DC to 20kHz than to 60Hz? > (Nice small ferrite transformers instead of big iron ones.)There's still the problem of local distribution. (Check out the meaning of "low voltage" in power distribution.) That would probably necessitate a non-redundant star system, without recourse to alternate feed paths.>> I suppose that when all signaling lines are optical, inductive >> coordination won't be an issue, but it would be as long as we use >> copper telephone circuits. > >> Bad idea. :-( > > Dielectric loss in air should still be low, but radiation would > have to be considered. So far it doesn't look good, but I am > not sure everything has been considered yet.Not only radiation (and brush discharge!) at the usual spacing of high-tension lines, but phase effects in a power grid. A wavelength at 20 KHz is a little under 10 miles (15 Km in air, less on a line). It would be hard to match phase at the ends of lines taking different routes. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●October 30, 20082008-10-30
Vladimir Vassilevsky wrote:> > > Glen Herrmannsfeldt wrote: > >> The question is, what would be the advantages and disadvantages >> to switching to 20kHz power from 60Hz? > > All losses will be greater by orders of magnitude. Skin effect, > capacitive/inductive spillage, losses in the core, switching losses, > rectifier losses, etc. > >> How much more efficient are ferrite transformers at 20kHz than >> our usual silicon steel power line transformers? > > It depends. There is no fundamental difference. > >> Assuming >> one uses superconducting DC power lines, how much easier is it >> to convert from DC to 20kHz? How much more efficient are various >> SCR based power controllers at 20kHz? > > SCRs won't work at 20kHz. The valid switching elements for that > frequency are FETs, and, may be, IGBTs. > >> How much would 20kHz to 60Hz >> converters cost? > > A lot :) > >> Most likely not practical, but there will have to be big >> changes in energy use in the coming years to reduce the >> global warming contributions. More efficient use of electrical >> power would help. > > What could make sense is switching to the DC power, like they did in the > modern aircrafts. The problem is the electrolitic effects destroying the > wiring.How about reversing the polarity on alternate days? Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●October 30, 20082008-10-30
Eric Jacobsen wrote:
...
> Both omegas look like question marks to me, but the degree and mu are
> fine.
Some extended ASCII symbols for the record:
Name hex Decimal (keypad)
� Degree Sign U+00B0 Alt+0176
� Plus-Minus Sign U+00B1 Alt+0177
� Superscript Two U+00B2 Alt+0178
� Superscript Three U+00B3 Alt+0179
� Micro Sign U+00B5 Alt+0181
� Superscript One U+00B9 Alt+0185
� Masculine Ordinal Indicator U+00BA Alt+0186
� Vulgar Fraction One Quarter U+00BC Alt+0188
� Vulgar Fraction One Half U+00BD Alt+0189
� Vulgar Fraction Three quarters U+00BE Alt+0190
� Multiplication Sign U+00D7 Alt+0215
� Latin Small Letter Sharp S U+00DF Alt+0223
� Division Sign U+00F7 Alt+0247
These should be OK with most ASCII fonts.
Jerry
--
Engineering is the art of making what you want from things you can get.
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Reply by ●October 30, 20082008-10-30
Jerry Avins wrote:> Vladimir Vassilevsky wrote: >>> What could make sense is switching to the DC power, like they did in >> the modern aircrafts. The problem is the electrolitic effects >> destroying the wiring. > > > How about reversing the polarity on alternate days?I am not sure what is the reasonable rate of the polarity reversal to prevent the electrolysis (vs power voltage). Another problem could be the transient on the polarity reversal, especially if the whole power grid has to be inverted. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
Reply by ●October 31, 20082008-10-31
On Thu, 30 Oct 2008 10:50:11 -0400, Jerry Avins <jya@ieee.org> wrote:>Eric Jacobsen wrote: > > ... > > > Both omegas look like question marks to me, but the degree and mu are > > fine. > >Some extended ASCII symbols for the record: > Name hex Decimal (keypad) >� Degree Sign U+00B0 Alt+0176 >� Plus-Minus Sign U+00B1 Alt+0177 >� Superscript Two U+00B2 Alt+0178 >� Superscript Three U+00B3 Alt+0179 >� Micro Sign U+00B5 Alt+0181 >� Superscript One U+00B9 Alt+0185 >� Masculine Ordinal Indicator U+00BA Alt+0186 >� Vulgar Fraction One Quarter U+00BC Alt+0188 >� Vulgar Fraction One Half U+00BD Alt+0189 >� Vulgar Fraction Three quarters U+00BE Alt+0190 >� Multiplication Sign U+00D7 Alt+0215 >� Latin Small Letter Sharp S U+00DF Alt+0223 >� Division Sign U+00F7 Alt+0247 > >These should be OK with most ASCII fonts. > >JerryThey all look fine here! This one: � Latin Small Letter Sharp S U+00DF Alt+0223 Looks like a beta or the German double S. Eric Jacobsen Minister of Algorithms Abineau Communications http://www.ericjacobsen.org Blog: http://www.dsprelated.com/blogs-1/hf/Eric_Jacobsen.php
Reply by ●October 31, 20082008-10-31
On Thu, 30 Oct 2008 10:47:33 -0400, Jerry Avins <jya@ieee.org> wrote:>Vladimir Vassilevsky wrote: >> >> >> Glen Herrmannsfeldt wrote: >> >>> The question is, what would be the advantages and disadvantages >>> to switching to 20kHz power from 60Hz? >> >> All losses will be greater by orders of magnitude. Skin effect, >> capacitive/inductive spillage, losses in the core, switching losses, >> rectifier losses, etc. >> >>> How much more efficient are ferrite transformers at 20kHz than >>> our usual silicon steel power line transformers? >> >> It depends. There is no fundamental difference. >> >>> Assuming >>> one uses superconducting DC power lines, how much easier is it >>> to convert from DC to 20kHz? How much more efficient are various >>> SCR based power controllers at 20kHz? >> >> SCRs won't work at 20kHz. The valid switching elements for that >> frequency are FETs, and, may be, IGBTs. >> >>> How much would 20kHz to 60Hz >>> converters cost? >> >> A lot :) >> >>> Most likely not practical, but there will have to be big >>> changes in energy use in the coming years to reduce the >>> global warming contributions. More efficient use of electrical >>> power would help. >> >> What could make sense is switching to the DC power, like they did in the >> modern aircrafts. The problem is the electrolitic effects destroying the >> wiring. > >How about reversing the polarity on alternate days? > >JerryWell, it's not DC any more then, is it? ;) Eric Jacobsen Minister of Algorithms Abineau Communications http://www.ericjacobsen.org Blog: http://www.dsprelated.com/blogs-1/hf/Eric_Jacobsen.php
Reply by ●November 2, 20082008-11-02
Eric Jacobsen wrote:> On Thu, 30 Oct 2008 10:50:11 -0400, Jerry Avins <jya@ieee.org> wrote: > >> Eric Jacobsen wrote: >> >> ... >> >>> Both omegas look like question marks to me, but the degree and mu are >>> fine. >> Some extended ASCII symbols for the record: >> Name hex Decimal (keypad) >> � Degree Sign U+00B0 Alt+0176 >> � Plus-Minus Sign U+00B1 Alt+0177 >> � Superscript Two U+00B2 Alt+0178 >> � Superscript Three U+00B3 Alt+0179 >> � Micro Sign U+00B5 Alt+0181 >> � Superscript One U+00B9 Alt+0185 >> � Masculine Ordinal Indicator U+00BA Alt+0186 >> � Vulgar Fraction One Quarter U+00BC Alt+0188 >> � Vulgar Fraction One Half U+00BD Alt+0189 >> � Vulgar Fraction Three quarters U+00BE Alt+0190 >> � Multiplication Sign U+00D7 Alt+0215 >> � Latin Small Letter Sharp S U+00DF Alt+0223 >> � Division Sign U+00F7 Alt+0247 >> >> These should be OK with most ASCII fonts. >> >> Jerry > > They all look fine here! > > This one: > > � Latin Small Letter Sharp S U+00DF Alt+0223 > > Looks like a beta or the German double S.It is what in German is called ess-tzet (however spelled) and I use if for beta because I can pretty well count on it reproducing. "Micro Sign" will also reproduce where "Greek Letter Mu" doesn't. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
