Slashdot Mirror
Disentangling Facts From Fantasy In the World of Edison and Tesla
dsinc writes "Forbes' Alex Knapp writes about the Tesla idolatry and confusing his genius for godhood: 'Tesla wasn't an ignored god-hero. Thomas Edison wasn't the devil. They were both brilliant, strong-willed men who helped build our modern world. They both did great things and awful things. They were both brilliantly right about some things and just as brilliantly wrong about others. They had foibles, quirks, passions, misunderstandings and moments of wonder.'"
Tesla > Edison.
Which is precisely what TFA is addressing.
AC was much better for transmitting back then because transmitting high voltage is more efficient (less current means less copper and less resistive waste) and they had an efficient way of converting high voltage AC to low voltage AC (transformers). Efficient high voltage DC-DC voltage conversion was not something that was possible back in the day.
DC is actually more efficient for long distance high voltage transmission -- they just didn't have the technology to convert DC voltage. Now days HVDC transmission for new long distance lines is much more viable.
For modern high-voltage transmission, capacitive losses matter even at 50/60Hz. HV transmission is best done as DC. The thing Tesla was right about was that with technology available back then, AC distribution was the only feasible one. It has only been in the last few decades that we have the semiconductor technology that would allow completely solid state, DC-to-DC power conversion all the way to the consumer. That would be, ultimately, the way to go. DC-to-DC converters can be quite compact compared to 50/60Hz transformers, especially when running at high frequencies. I've seen resonant converters taking in 10kV 3 phase and outputting 1.5kV DC at about 50kVA. It had PFC as well. Two people could very easily lift one up, it was probably less than 200lbs, just bulky, and the magnetics (cores) could fit in a breadbox. Try lifting up a 50kVA oil immersed transformer with same ratings -- it's half a ton, give or take.
Alas, circuit breakers for DC are significantly more complex and expensive than ones for AC, since you have an arc that needs to be quenched. They need to have a chamber that utilizes spatial gradients in pressure or temperature (due to asymmetry of the plasma chamber) to move some air around to blow the arc out. AC arcs are usually self-extinguishing, except at extreme short-circuit currents and voltages (high voltage substations and the like).
A successful API design takes a mixture of software design and pedagogy.
Yes, and Nikola Tesla was simply wrong in promoting alternating current for about any use. If you look at modern electrical or electronic gear, they all have circuitry to convert alternating current to direct current before powering anything.
EXCEPT for the AC electric motor and the florescent light bulb -- two of the most common uses of power even today (and certainly before about 1960). In 1960 the refrigerator, the record player, the kitchen mixer and also various household pumps were powered by what was essentially a slightly improved version of Tesla's motor. The incandescent lights were also being run off his power too. Only really the radio needed a coil to convert to DC.
But it was legitimately a problem back in the day. The reason was twofold:
1) There's no good way to generate DC using a mechanical system. So while something like a solar cell will generate you DC, a mechanical generator won't, at least not without some fiddling and then not as efficiently as AC. These days, not a big deal, we have good devices to convert from one to the other quite efficiently. However when the current wars were happening, DC generation wasn't as good as AC generation. You see it to this day: Cars use alternators (as in alternating current) to generate power, despite being DC devices. The alternator then has a rectifier bridge to turn it in to (pulsed) DC power, which the battery helps clean up.
2) There was no good way to convert DC voltage. AC is exceedingly easy to convert with simple technology: A transformer. You can step it up or down with some wraps of wire, and it is fairly efficient to boot. No such luck with DC. There just isn't a good way to step it up with the technology they had back then. As such you needed generators close to the home. You couldn't run massive voltages, far too dangerous (and as a practical matter difficult to generate directly) and you couldn't go for long runs because of impedance loss. These days thyristors can do the trick nicely but they are 1950s tech, and the ones that can do HVDC are more recent.
Were we to rebuild the grid these days, DC might well make sense (though it does have some other issues that need to be considered). However during the current wars, Tesla really did have it right. The technology was there to make AC work well, not DC.
Edison really was fighting for DC because of his invested infrastructure, not because it was a superior technology at the time.
While true, it's also misleading. The inverse square law isn't magic, it's follows naturally on from basic geometry. If you take a 2D beam with any angle of spread, then at distance 2n from the source, it will be twice as wide as at distance n. If the beam is in three dimensions, then the spread will be twice as wide in each dimension, so it will be covering four times the area. This applies just as much to flashlights as to lasers, but it's not nearly as important in the latter case as the former because going from a radius of, say, 1mm at one km to 2mm at 2km doesn't really make much difference to the brightness, while going from 10cm at 1m to 20cm at 2m does.
With things like phased array antenna, it's possible to get the beam spread quite low, with lasers you can get it very low. The problem is not the inverse square law, it's that at the kind of power and directionality you want for this kind of thing you end up with something that has no problem propagating the power efficiently to the destination and will happily burn a hole through anything that tries to prevent it from doing so.
I am TheRaven on Soylent News
Oh, but it was. The U.S. film industry being based in Southern California is due in large part to that fact.
Please stand clear of the doors, por favor mantenganse alejado de las puertas
He had a huge staff who did the vast bulk of his R&D and a significant % (possibly the majoroty) of his achievements were actually made by his staff with Edison just facilitating their efforts and then claiming the kudos.
I want a list of atrocities done in your name - Recoil
For modern high-voltage transmission, capacitive losses matter even at 50/60Hz. ....
That's an overly broad statement. Capacitive reactive losses really matter a lot on submarine or buried cable. Not much of a factor in overhead HV transmission. Think of it like the classic parallel plate capacitor - since that's what we have, just our "plates" are curved away from each other (which reduces capacitance, but let us consider them as flat here). The area (over the length of the lines) is large, yes. But what kills that off so to speak, is a product of two things: a poor dielectric medium (air) and a large distance (many meters) between the "plates".
For "plates" 3cm wide with a length of 1km and a separation of 10m: about 27pF. In other words: 27pf/km.
Formula: (where's my dang MathML slashdot?) C = k * E * A / S where:
C is capacitance in Farads
k is relative permittivity of the dielectric. Equals 1 (for air)
E is permittivity of space, a constant 8.85E-12 F/m
A is area in meters squared
S is separation distance in meters
For that 1km model above the impedance at 60 Hz is 100Mohm. For a 220KV line that is a loss of about 480W/km. Such a line would be conveying power in the few hundreds megawatt range. Not much of a reactive loss there. Different on sub/buried: k is much larger, and S is much smaller (mm - cm distances).
he was NOT a patent troll, since he BUILT the stuff he patented.
I'd would agree that he was a patent asshole, though.
This is ignorant. Yes he bought QDOS, and yes he had people working for him to modify it. This doesn't take away the fact that he was heavily involved in building the BASIC that was loaded into PROM on my PC-1! For the first several years of the company Bill coded. He also was very astute at guiding the financial and business aspects of his company, and being at the right place at the right time multiple times. Don't forget that he pointed IBM at Digital Research FIRST, before he went and purchased QDOS. At the time - Microsoft was a language company. They specialized in creating language compilers. That is how IBM had Pascal, etc. available for the PC the first day it was introduced!
GAWD - you're making me defend Bill Gates - STOP THAT! (Now I've got to go and compile a linux kernel or something to make up for this!)
Have you compiled your kernel today??
he was NOT a patent troll, since he BUILT the stuff he patented.
True but he was a different kind of patent "troll". For example with the light bulb once Swan had patented his design in the UK Edison submitted a almost direct copy for patenting in the US and then tried to sue Swan for patent infringement in the UK! The two eventually settled out of court with Swan running the UK side of things and Edison in the US. So by today's standards he was not a troll but he was certainly some sort of unpleasant creature living under the patent bridge - a patent orc perhaps since he liked to raid others patents and got away with it due to his wealth?
Here's a great response to the forbes article, from the author of the article that the Forbes article is critiquing:
http://theoatmeal.com/blog/tesla_response
- Spryguy
There are three kinds of people in this world: those that can count and those that can't