Who Invented Three-Phase?

They were using diodes industrially in 1890?!

Sheesh.

Smoother rectification was a spinoff that happened decades after the system was up and running.

Silly question: Is there any advantage to using more phases for power transmission or motors than the standard three phase power, such as 5 phase or 7 phase? There's an obvious disadvantage - more wires, more transformers = more things to break.

Did any of the early experimenters experiment with anything weird like 5 phase power?

Yes-- if you're turning it into DC you can reduce or eliminate the need for filtering, and electrolytic caps are prone to failure before most any other bit.

For Tesla maybe, but three phase was patented elsewhere as I have pointed out.

al

not

The best compromise for least copper is 3 phase. Just as 50-60Hz is best for the frequency. Any higher and the transformers are smaller but there are more line losses. Any smaller and you get flicker on the lights and the transformers get bigger!

Hardy

Maybe some more. You only need the three legs (or three transformers). The additional delta secondaries are wound on the same legs. Since the secondary currents split between the secondary windings, each one can be wound with smaller wire and take up about the same length on the core as a single winding feeding a six pulse supply.

I did. You want to buy it?

Send money.

John

Good analysis of the history of electrical power.

Before Edison promoted electricity as a power source, typical factories used water power or a single steam engine coupled with leather belts to drive devices like saws, grinders, lathes, mills, etc.

As high starting torque, single phase motors were not available, Edison promoted D.C. over A.C.

Although Tesla cultists think that Tesla had a falling out with Edison because of money, it is more likely that he went to Westinghouse because of their differences about the immediate future of A.C. and D.C. motors in industry.

Tesla had a great respect for Edison, and acknowledges that he learned a lot from him.

Considering that Tesla had access to Edison's technology and joined with a competitive company, it seems to me that Edison had more to complain about than Tesla.

The difference between Edison and Tesla was that Tesla had a fixation on A.C. which he understood better than anyone else, whereas Edison had customers and investors to satisfy, and he couldn't wait for the A.C. technology to catch up. Westinghouse probably linked with Tesla and promoted A.C. because Edison controlled most of the patents on D.C.

Edison was like Steve Jobs, in that he had a better feel for what was possible and the marketplace.

Note that Edison not only ushered in the electric age, he invented audio and video recording.

In fact, although he also had investors to satisfy, Tesla's wasted a lot of his money and investor money on his flights of fantasy.

Being practical and market driven, the Edison companies switched to A.C. as A.C. technology improved,

but A.C. technology never evolved to the point where Tesla or anyone could beam practical amounts of power from power stations to users.

It would be nice to beam power to all these gadgets ( Ipads, phones, cameras, flashlights, GPS, etc.) and not have to recharge them.

The following URLs display torque curves of various kinds of A.C. and D.C. motors.

As "m II" indicated, the initial purpose of multiphase was to get a rotating magnetic field rather than to distribute power.

But there isn't anywhere practical where anything otehr than 3 phase,

Hardy

But there isn't anywhere practical where anything otehr than 3 phase,

Hardy ============================================== DC is very practical. My phone isn't polyphase or < 100 Hz, there isn't anywhere practical where anything other than DC is used. The step from transformer to charged battery is trivial, it is called "rectifier". A schoolboy could work it out.

--Androcles

Actually DC is making a resurgence for efficient long distance, high = voltage=20 transmission, as it is now very easy to convert DC voltages up or down.=20 Three phase AC motors are also being found increasingly in small = appliances=20 such as washing machines and food processors, and they first rectify the =

incoming AC to DC and then use PWM to create three phase. Most = electronics=20 now use switching supplies which rectify the AC, and would be even more=20 efficient if powered directly from DC. Lighting and heating work as well = on=20 DC as AC. And DC is somewhat safer than 60 Hz AC which is just about the =

most dangerous frequency for causing fatal ventricular fibrillation.

Paul

ical

, not

But if it's not divisible by three, it drives you crazy until you take steps to have it changed.

The real question is: why didn't Tesla fight for 66Hz? IT'S ONE LOUDER.

I always ask: what was the problem Tesla was supposed to fix?

Apparently he and another guy redesigned all the Edison equipment. Earlier it had resembled horse-shoe magnets with a rotor between the tips. Later it resembled small cylinders spinning within bigger ones.

Did Tesla do that? If so, then not only did he fill the world with induction motors. Perhaps he also filled it with DC motors shaped like cylinders. Tesla, as an accidental sculptor, seemed obsessed with lathe-turned shapes.

Don't forget that his training was in mechanical engineering.

Find Norbert Weiner's autobiography "I am a mathematician" for some interesting dirt on Heaviside's invention of transmission line theory and "Telegrapher's equation." It's another example of weird loner geniuses screwed by large corporations. M. Pupin patented Heaviside's breakthrough, taking the credit (and the huge payment) for making long- dist comms possible. Weiner tells all, and spits on Pupin's grave. Preeces' also!

:)

I love the story of the transistor: Shockley told his employees Bardeen and Brattain to stop wasting time on the point-contact transistor. So they put it all on a wheeled cart, and kept working on it. That way they could easily hide it in the disused adjacent office whenever Shockley was scheduled to be in the lab. "Crystal Fire," great book.

Actually DC ======================================== Don't snip the context or you'll be snipped in return.

Hardy ========================================

Interesting to look at old mechanical power installations. Long jackshafts going through the building with pulleys for power takeoff.

AC was not considered useful. There weren't ANY AC motors.

Apparently Tesla biographers are cultists. They say the falling out was about not getting paid what Tesla thought Edison had promised. Tesla was so mad at Edison he left without a job prospect and wound up as a ditch digger for a while. Westinghouse was much later, after Tesla set up a laboratory and applied for patents.

I don't think so.

Fiction.

When Tesla worked for Edison, Edison did not understand advantages in AC and dismissed it entirely. Not having an understanding of science he opposed it as it later as AC plants were being installed.

He also opposed it because of his dominance and investment in the DC power field.

In addition to competing with Edison, Westinghouse saw the advantages in AC.

Tesla has all the basic patents for AC motors. You essentially couldn't make an AC motor without infringing on a Tesla patent.

Tesla also has basic patents in wireless/broadcasting. Marconi infringed. The decision on Tesla priority was not made (US Supreme Court) until after Tesla died. I believe you can't make a practical radio without infringing on a Tesla patent (maybe you can with modern ICs).

Tesla was an inventor, but not a good businessman.

Tesla did have some 'different' ideas. On the other hand, much of what he worked on was in unknown fields.

A gross oversimplification. There were lawsuits and eventually compromises. By then Edison had been forced out of his company.

Westinghouse also was forced out of his company.

Also, (relatively) short-distance undersea cables, where losses would be dramatically higher if AC were to be used.

For example:

Well, for one, the transmission distance problem. Edison's DC could get only about half-way across town before the wire resistance dropped so much voltage that the load couldn't operate properly, like, light bulbs wouldn't get above dull red and so on.

So Tesla invented AC and the transformer.

The Tesla coil is kinda the "logical" extension of transformer theory; remember, back in those days they were inventing all this stuff from scratch - they were the "pioneers," to boldly go where no man has gone before and all that.

So, with a step-up transformer, you get a higher voltage for transmission, and the current drops. Well, at 100,000 volts it only takes 10 mA to transmit a kilowatt. At a million volts, it takes only a milliamp - at a billion volts, a nanoamp, and so logically, if he could get an infinite number of volts, you shouldn't need any wire at all!

Unfortunately, he ran into that little problem where the electrons like to escape from the high voltage. )-;

Cheers! Rich

At least one of the massive Detroit area auto plants used to provide their own 6-phase. (?Willow Run?) This when it had its own power-house.

Maytag's Neptune washers used 6-phase motors.

There are some interesting opinions on this:

In the early days, there were frequencies as low as 16-2/3 Hz, 25 Hz, = and 45=20 Hz. It was easier to build generators that ran at slower speeds, and = large=20 low speed high torque industrial motors. Higher frequencies required = more=20 poles and thinner laminations which were more difficult to make in the =

The last reference above includes a lengthy and seemingly accurate=20 assessment of the choice of frequency. It claims that Westinghouse=20 originally used 133.3 Hz.

There may also be a relationship to phonograph record turntable speeds = of=20

There is also an interesting theory that 60 Hz was chosen as the most = lethal=20 frequency for the electric chair, although Edison may have started this=20 rumor when he was expounding on the dangers of AC vs DC.

The perceived loudness of AC hum is also a consideration, and 50/60 Hz = is=20 relatively well tolerated, but 100 Hz or higher is much more = objectionable.

Paul=20