Why 60 Hz or 50 Hz

Why is house current 60 Hz in the US?
Why is it 50 Hz in other parts of the world?

Is there some mathmatical formula that states that 50 and 60 Hz are the most efficient frequencies for power transmission?

I am reading a book about Edison and Tesla and the fight they had regarding how to generate electricity in the US (DC vs. AC).
Tesla was the AC proponent. At one point he told the engineers at Westinghouse that 60 Hz was better than what they were using (133 Hz). I was wondering why. ---Marc


I had trouble deciding where to post this question, so I put it in the Cafe.

I love things like this. Did a quick look on google and it appears that anything lower than that caused flicker in incandescent lights, which were one of the first applications.

On a related note, did anyone else used to like the PBS TV series "Connections"? It would start a story hundreds of years ago and follow it to show how a series of events led to things like air conditioning. Great show.

Joe

Joe---If flicker was the issue then Tesla wouldn't have told the engineers to LOWER the frequency from 133 Hz to 60 Hz. There has to be another explanation.

And "yes". I was a big, big fan of Connections. I bought the book and used it as a resource for many papers in college. I never did get to see the sequel series, though. I wonder if it is available on disk.......
Going to check BN.com.........

Yes, I too liked Connections. In fact most of the documentary type series on PBS are awesomely good. I think most are made in Boston at WQED. Otherwise stay away from PBS, their political philosophy will rot your brain. /ubbthreads/images/graemlins/smile.gif

I believe the first AC was used to bring power from Niagara Falls to Buffalo to power the mills. It's original purpose was to turn motors, not power lights. Tesla and Westinghouse developed it. Actually there were two competing proposals to get the power from the falls to Buffalo. The other one envisioned about 20 miles of leather belts and pulleys. Some thought this was more practical, but in the end, Tesla's scheme was implemented.

Edison used low voltage DC to light cities, but because of the low voltage, there needed to be a generating station every few blocks. When he heard of Tesla's high voltage plan he wrote his congressman to try to prevent it. He claimed the high voltage was too dangerous. I suppose if AC were invented today and a proposal to run 7000 volt lines on poles along the road were made, one of the jackboot type agencies in Washington would prevent it.

The original frequency was 25 Hertz. It worked for motors but caused lights to flicker. Subsequent generating stations at Niagara Falls switched to 60 Hertz for this reason. There was a 25 Hertz generating station at the Falls until sometime around 1960, when a rock slide demolished it. After much debate, I believe it was replaced with one generating 60 Hertz, and the users of the 25 Hertz power had to rewind their motors.

Saw part of the Connections sequel series, stopped watching, was not even close to the original. I've got the book in the basement, will have to dig out and reread. Let me know if you find the original series on DVD.

Have no idea about the 133 -> 60 hz deal.

Eluminator, you're right, when PBS does a true documentary, leaving out their political agenda, they can be very interesting.

Joe

Marc, search google groups for "tesla 133 60", lots of info there.

One person proposes that Tesla preferred 60 hz because...

"The 60 Hz must come from its easy division into a 360 deg circle. Since the frequency is basically decided by the rpm of the dynamo at the power plant, 60 Hz would vastly simplify calculations, etc."

Joe

I had also heard we went with 60hz for the mathematical reasons. 50 in to 360 is just to complicated /ubbthreads/images/graemlins/smile.gif I think it also makes 3 phase simpler somehow?

One sixtieth of a second is also an extension of the way the hour is subdivided.
<ul type="square">[*]60 minutes in 1 hour
[*]60 seconds in 1 minute
[*]60 cycles in 1 second (at 60 Hz)[/list]
Paul

I read here "that 60Hz was originally selected by Tesla for obvious reasons, and that 50Hz was selected because it's the minimum frequency at which incandescent light bulbs will work well. Later, GE & Westinghouse in the U.S. standardized on 60Hz possibly to preclude competition from European manufacturers."

[ QUOTE ]

50Hz was selected because it's the minimum frequency at which incandescent light bulbs will work well.

[/ QUOTE ]
This is poorly worded. We all know, after all, that incandescent bulbs will work at 0 Hz; i.e. direct current. Perhaps they are talking about the issue of flicker, which would be governed by the thermal time constant of the bulb filament.

My old Grandpappy (Whiskypapa1, a turbine/generator engineer for GE from 1895 to 1950) said it was the upper limit for the iron alloys used in the transformers and motors at the end of the 19th century.