There was a Westinghouse 133-1/3 Hz system in Pittsburgh. Not sure whether it dates from before or after Niagara Falls. Once in a while you see a
133-1/3 hertz electric fan on eBay.
There is still a tiny bit of utility supplied 25 Hz in metropolitan Buffalo, NY. This service will be permanently discontinued in January 2007.
It is generally forgotten that much of the Western US was originally supplied with 50 Hz. Certain locales in Southern California actually changed frequency twice. Some areas south of LA were originally supplied by 60 Hz local plants. When Hoover Dam was built it provided 50 Hz and these localities were changed to 50 Hz. However, in 1938 Hoover was changed to 60 Hz and these disticts were converted back!
The correct answer is that only some generators spin 3600 rpm. Not every power producing generator is driven from a high speed gas or steam turbine. It all depends on the number of poles (and, of course, the line frequency).
The higher the rpm, the more expense must be designed into the machine to prevent the centrifugal forces from literally forcing the machine to fly apart. Big machines + high speed = lots of stress
Most diesel gensets run at much lower rpms. 1800 rpm is typical.
The nominal speed for the hydropower generators at Bonneville Dam on the Oregon/Washington border range from 257, 156.5, 75 to 69.2 rpm.
I doubt that the engineers who designed these generators were discouraged because the math calculations were "hard" and did not come out to nice round values.
Some of their electrical experiments are scientifically questionable, and done more for effect. They used a high-voltage generator which threw a continuous arc to the string. A Tesla coil would have produced more realistic "lightning".
On Fri, 10 Mar 2006 20:03:59 GMT, Rich256 Gave us:
If you think that ALL of a multi-million volt lightning bolt would travel down a piddly little string, then it is YOU that have had you brain fired.
Myth Busters got the "hair drier in the bath tub" job wrong as well. They did not construct the "heart sensor" correctly, by a long shot.
They have made several incorrect assumptions, and their "physics" as well as their"engineering" has been off many times, though they usually get it right.
I didn't say I thought it. That is what they said. Looked to me like they had a lot more than a "piddly little string". Of course it doesn't take "multi-million" volts to kill.
They had a kite with a "lightening rod" on it to what looked like a pretty heavy sting that they wet down. The "string" looked more like a twine rope.
Then, as Ben Miller said, they used a high voltage generator to throw an arc at the kite and the string was not as long as it might have been. I forgot what they did to determine that the jolt would be fatal. What ever they used their conclusion was that there was enough current to kill.
As I said, I saw a lot of things that didn't look valid. They couldn't even get a kite made to Franklin's design (a square one) to fly.
They measured some pretty high voltages apparently generated by the wind when the kite was airborne but not enough current to create a spark.
On the other hand if lightening happened in the vicinity of such a kite with a wet string, the air around the string might well become ionized creating a preferred path to ground.
Lightening does strange things. A good friend was sitting on a metal chair fishing. Only a tiny cloud nearby. He suddenly found himself on the ground. First thought he had a heart attack (which he had before). Then he smelled something burning. It was the back of his shirt and pants. The chair laid nearby a molded mass. He took the "evidence" to work thinking no one would believe him. Even the backs of his shoes had split.
--------------- Note that the pole pitch for a 3000rpm N pole 50Hz machine, in terms of degrees, is the same as for a 3600 rpm, N pole, 60Hz. machine. In other words if the pole pithc is 180 mechanical degrees for one, it is the same for the other. Speed in rpm and degrees in a circle are not related.
On Sat, 11 Mar 2006 03:12:52 GMT, Rich256 Gave us:
Multi-million volts will NOT kill if there is no current flowing. Voltage isn't what kills. Current flow "through the heart" kills. High currents can kill by way of burning, and extreme damage to the flesh along the current pathway, but the usual result that causes death is a fibrillation of the heart.
With a set of shock paddles, up to several hundred joules are required to be dumped into the victim/patient to restart the heart using a defibrillator.
In OPEN heart surgery, they use tiny little paddles, and only a few milliamps to get the same job done.
Externally, the current has to pass through the entire body in order for that same "couple of milliamps" to actually hit the heart. While exposed, the current can be applied directly, and the requisite is much lower for the same effect.
Hell, they probably used a friggin wire. I have seen them make more than one errant choice for a test before. Ben's was likely several hundred feet up in the air as well.
The voltage applied was much different as well in that case. As he also stated, they would have had a much more realistic simulation had they used a Tesla coil.
There have been many lightning victims that have survived direct hits. No strings attached.
All that matters is the current, but if their test conditions are wrong, their conclusions are not valid.
One needs wind, and a nice thunderstorm would help.
You reversed it again. The voltage creates the spark. Think "pressure". Upon said creation, THEN current flows. Although with lightning a LOT of current flows long before one even sees a visible bolt occur.
If the water and string were conductive, there would not only be no need for an ionized air pathway, but the lower resistance string would carry current quite easily without it. Path of least resistance and all... ya know.
No shit. I have seen ball lightning... so I know this to be true.
My grandfather was standing on the back porch when a bolt big enough to set our roof on fire hit it. He jumped six feet, and it wasn't from the sound of the crack.
He was the victim of a lightning strike. He survived.
60 cycle was chosen because 60 was an "even" fraction of 360 degrees of a circle and it made engineering motors, generators, etc., etc., simpler mathematically and manufacturing-wise.
50 cycle was chosen 1) because 50 was an even fraction of the metric "100", and there was the principle of clean decimal things. no matter how much extra d__ work it was. 2) and while using an "even" fraction of "100" made rotational engineering caculations more difficult in most countries, the French (who had developed metric as part of their 16-17th century war-stopping French-as-the-universal-communication-language-of-court-and-standards push and have been pushing the hell out of it ever since), had their circles in a deci-based 100 divisions, so 50 was easier than 60 for French engineers. 3) using 100 rather than 50 had technical and cost problems.
or so I heard.....
FWIW - And there was also some word about Edison doing experiements with vison and his moving picture machines, that had 60 as a desirable decile number just above human discerning level- e.g., 50 cycle fluorescents used to flicker in the eyes when seen off to the side in a fair percentage fo the population, while 60 cycle flickers are only seen by a very small percentage of the populace.
Flicker was a given with the early motion pictures. That is why they are also known as "Flicks". The tradeoff is not to have to run the film too fast (and waste film) vs. still give a realistic illusion of motion.
Before 24 frames per second was chosen, there were standards for slower rates down to 18 frames per second. This is why many old movies appear to be almost comically speeded up when run on modern projection equipment at normal speed.
Even after standardization at 24 fps, the flicker in a movie theatre was very objectionable. The solution was to use the mechanical shutter on a projector to flash each frame onto the screen twice or the equivalent of 48 per second. It is interesting to note that this, along with the specific spacing of the sprocket holes, has been an unchanged worldwide standard for 100 years.
When television was invented, there was a further problem if a film was to be projected on TV because the frame rate of film was 24 fps and US NTSC TV had a standard of 30 fps, interlaced and made up of two fields with an effective field rate of 60 fields per second. The field rate was made synchronous with the US power system frequency of
60 Hz, as this was the most accurate time base available with the technology of the time.
The problem was solved by cleverly flashing the first frame of film twice and the subsequent frame three times. This alternating sequence continued and magically allowed the film frame rate of 24 fps to match the scanning frequency of 60 fields per second.
On Sat, 11 Mar 2006 21:41:46 GMT, not snipped-for-privacy@xxx.yyy (Beachcomber) Gave us:
Bullshit. Any difference would be compensated for, just like it is today when showing standard 24 fps films on 30 fps TV. Six frames every second are duplicated.
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