Who Invented Three-Phase?

A case can be made that switched reluctance motors are N phase.

And highly likely to shoot the induction motor out of the saddle.

Beats them all to hell on efficiency, lower rpm torque, self-starting, and variable speed. But you have to get sneaky to avoid physical feedback sensing devices. Also some stability issues.

THE AGE OF ELECTRICITY. by Nikola Tesla

"Now I come to an interesting chapter of my life, when I arrived in America. I had made some improvements in dynamos for a French company who were getting their machinery from here. The improved forms were so much better that the manager of the works said to me: "You must go to America, and design the machines for the Edison Company." So, after ineffectual efforts on the other side to get somebody to interest himself in my plans financially, I came to this country. I wish that I could only give you an idea how what I saw here impressed me. You would be very much astonished. You have a? undoubtedly read those charming Arabian Nights tales, in which the genie transports people into wonderful regions, to go through all sorts of delightful adventures.

My case was just the opposite. The genie transported me from a world of dreams into one of realities. My world was beautiful, ethereal, as I could imagine it. The one I found here was a machine world; the contact was rough, but I liked it. I realized from the very moment I saw Castle Garden that I was a good American before I landed.

Then came another event. I met Edison, and the effect he produced upon me was extraordinary. When I saw this wonderful man, who had had no theoretical training at all, no advantages, who did all himself, getting great results by virtue of his industry and application, I felt mortified that I had squandered my life.

I had studied a dozen languages, delved in literature and art and had spent my best years in ruminating through libraries and reading all sorts of stuff that fell into my hands. I thought to myself, what a terrible thing it was to have wasted my life in those useless efforts. If I had only come to America earlier and devoted all of my brain power to inventive work, what might I have done? In later life though, I realized I would not have produced anything without the scientific training I got, and it is a question whether my surmise as to my possible accomplishment was correct.

In Edison's works I passed nearly a year of the most strenuous labor, and then certain capitalists approached me with the project to form my own company."

The likely cause of 45 RPM was the same as the big hole in the middle: RCA wanted to uniquely supply all of the product.

Two points here

1. the N phases are not supplied to the motor but created at the receiver end.

Hardy

It's too noisy at present though. Ok for a car maybe.

Not really, it's a series motor that is the universal one. A shunt wouldn't work on dc and ac. It works because Torque is prop to current squared and this is like a rectifier of sorts.

that

to

=46or series connected brush motors, perhaps. For induction motors, = speed is a function of frequency primarily.

Nope. Especially not with variable frequency drives.

You use three center tapped transformers. That gives you six phases at 60 degrees each. The center taps are tied together for the negative, and the common cathodes are the positive. As stated above, common of high power transmitters since it requires little filtering.

Electrolyic rectifiers were one of the first availible that would handle much curent.

Wanna bet?

Your phone only needs a few mA to operate, and the audio is superimposed on the DC supplied by your Telco. Kind of hard to do if it's AC powered, isn't it?

I see that everyone is pretty much wandering in circles here including Don Lancaster.

The Wiki answers are pretty much correct. All the rest is crap. Tesla did the calculation for transformers (which pretty much held for motors and generators too) for the best frequency for operation. No, it wasn't about phonograph speeds (they were spring motors then!) or mystical numbers, or thickness of laminations in the 19th century, or electric chairs, or how loud "hum" was (a particularly dumb assertion in an age of acoustic reproduction) It all had to do with (are you all ready for this?) MONEY! Put it in the formula. I want to put distribution transformers all over town. To attain a certain efficiency given the standard cheap Iron of the day and the amount of copper needed, what frequency is "best" meaning gives transformers that cost the least? Tesla calculated 60 Hz. Europeans are said to have chosen 50 for political reasons though I don't know what the politics was.

Today cheap iron can be made much better, but the frequencies have stayed the same by "inertia" I presume. Aircraft typically uses 400 Hz but takes expensive high quality iron. But there the object isn't cost, but weight. Modern switching supplies don't use iron at all and operate at very high audio frequencies.

As for Don's assertions about 45 Rpm records, he should be ashamed of himself for knowing so little of the history and technology of the 45 after writing so many popular articles for so many years. Sure Big Corp bashing is fun and typically true, but in this case... RCA worked on the 45 BEFORE CBS developed the 33 1/3 LP. Basically the idea was to develop the "ultimate" 78 rpm record. Which is to say a record that did everything the common 78's did and more. So changing to a vinyl record they reduced the diameter, and lowered the rpm so that the recording time of a 78 fit on a 7" record. This lowered weight, storage space, and cost of the records. To reduce material even further the records were made thin. But rather than a uniformly "floppy" record, only the outer band where the track was was reduced while the label area was left thicker. This made the record stronger and less flexible, but also provided the technical advantage of not allowing the recorded surfaces to rub against each other when stacked on a changer, hence reducing damage and improving record life.

The 45 speed was chosen because they wanted the recording "track" area to be relatively optimum. On a large LP when you get near the center the fidelity tend to get worse. This has to do with both the fact that the linear velocity of the needle over the track is lower but also in the case of vinyl due to the fact it is soft and tends to "give". This creates distortion as not the needle is not precisely tracking the original groove. To reduce these effects, RCA engineers upped the speed slightly (but still not so much as to not have the full 78 recording time) and also increased the spiral pitch along with increased cutter excursions. The latter was probably also done to allow the use of cheaper phonograph pickups in the players they sold. Later "extended" 45s were also pressed that used standard LP groove spacing (but still the same 45 rpm speed) to get more recording time on a 45. (Often for classical singles etc) The point is that much like the way Tesla came up with 60 Hz as the optimum transformer frequency, RCA came up with 45 rpm as the optimum record speed for maximum fidelity with a 7" single with a narrow track at the outside diameter. (given the state of various recording arts at the time). Eventually LP technology was improved to where even the most inner tracks produced quality reproduction.

Which brings us to that large hole that Don is pondering. It was NOT to "corner the market". Yes, RCA had the 45 and CBS had the LP, but pretty soon they both were making both kinds and as far as I can determine nobody sued anybody over it. The large hole had to do with how record changers worked. Old 78 record changers worked by placing a stack of records on a small diameter spindle that had an offset in it a few inches above the turntable. As each record was needed, it was shoved sideways off the offset to drop down onto the turntable. The small hole and tiny spindle generally created a pretty short life for the record hole when used on a changer. So RCA made the hole much larger and even better used the thicker label area to taper the label down to a thin thickness again at the hole. This meant that in a stack of records there were these V shaped grooves between records. A set of thin blades that came out from the large spindle held the stack up while the blades holding the bottom record retracted allowing it to drop. Hence, the ENTIRE changing operation was done right from the center spindle and the tapered gaps and blades and larger holes meant you could change these records forever without damage! Since the 45 standards insured all records had the same label thickness one didn't have the problems that 78 changers often had when dealing with records of differing thickness.

Remember that RCA/Victor also sold phonographs so if there was any market cornering, it was in that department.

So the bottom line was the old 78 record was totally perfected. Which not too many years later was about like building the perfect buggy whip. Life and times just passed it by.

RCA 45s? HELL! I was there!

..

that

to

I am not quite sure what you are saying, but the constant torque that I was speaking of was contant torque over the full duration of one cycle (1/60 second). In other words, the torque does not change based upon what the phase of the incoming signal is.

Yeah, I believe that. But inventions are built on previous inventions combined with need, so it is not surprising that several people would work in parallel.

A woman once tried to sneak a pistol into an Eric Clapton concert because she thought he was stealing songs from her on the astral plane. There's no law against astral theft, so she turned vigilante.

There were also mechanical rectifiers (and actually a DC dynamo's = commutator=20 is essentially just that)

Here's an article that shows how to make a full wave electrolytic = rectifier:

And a single phase version that glows and also has a negative resistance =

region which generates RF:

I seem to recall my father talking about such rectifiers that he built = as a=20 youngster for charging batteries.

Here is an article from 1909 about crystal rectifiers, and a Wiki = reference:

The Wiki article is interesting and there is a humorous picture of a man =

with a crystal radio in a corn-cob pipe and wearing an antenna!

Very interesting...

Paul=20

cal

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

It is, but long distant transmission is not trivial (or wasn't at the time).

Hardy

It is, but long distant transmission is not trivial (or wasn't at the time).

Hardy ================================================= It isn't far from the alternator to the battery in my car although a bridge rectifier is cheaper than a commutator. I've never heard of AC solar panels. DC is far more practical than AC, that's why there is so much of it. A schoolboy could work it out.

Actually it can be argued that solar panels are AC, with a period of 24=20 hours. And higher frequency components when clouds float past the sun or =

leaves blowing in the wind change the insolation. Every signal has an AC = and=20 a DC component, and most devices use AC to perform their function, while = DC=20 is mostly used for storing and perhaps transmitting energy. Digital=20 computers use clocks which are certainly AC, and sequential logic = consists=20 of alternating ones and zeroes. All modern communications use RF. Even = DC=20 motors produce a rotating magnetic field by means of a commutator or=20 electronics. Lighting and heating may be the only useful purposes where = DC=20 and AC are equally useful and efficient. And it could even be argued = that=20 thermostats and light switches convert the DC to AC with a very low and=20 variable frequency.

So, what's your point? Can your schoolboy provide a compelling answer?

Paul