The Y1936 Problem 7

[nate2003]

Here is an interesting article. Actually, this website has many interesting scientific/engineering articles.

http://www.americanheritage.com/articles/magazine/it/2000/3/2000_3_64.shtml

"I have had my results for a long time, but I do not yet know how I am to arrive at them." Karl Friedrich Gauss

 

[SlideRuleEra]

Good Article, that brings back a specific memory. On the final exam of a college electrical power course (in the late 1960's) we had a question that came from that same 50 CPS to 60 CPS conversion.

The question went something like this:
"During the change from 50 cps to 60 cps what had to done to existing transformers?"

I can not longer recall the electrical technical details why, but the answer, as I recall was "Nothing".
Having been designed for 50 cps, the transformers had "more than enough" iron for use at 60 cps. The practical result was that they operated at 60 cps just a little bit more efficiently than designed.

Hopefully some of the EE's here will set me straight if I have gotten mixed up on this issue.

PS: I know that Hz is the proper terminology for cycles per second these days, but this IS the History Forum

http://www.SlideRuleEra.net

 

[epoisses]

http://en.wikipedia.org/wiki/List_of_countries_with_mains_power_plugs,_voltages_and_frequencies

What a mess we made of it

 

[Zogzog]

Great article, Thanks!

 

[Ussuri]

I notice from the Wikipedia entry that the majority of Europe use 50Hz supply. Why did the US change from 50 to 60 Hz. Is there a big benefit?

 

[SlideRuleEra]

In late 19th & early 20th centuries there was a "frequency completion", sort of like VHS vs. Beta VCRs in the 1980's or Blu-ray DVD vs. HD-DVD today.

"Motor People" wanted DC - easy to build and control speeds of large motors for things like trolleys & factories. Since reasonable voltage DC cannot be distributed long distances efficiently, they were willing to settle for low frequency AC. 25 Hz was considered acceptable.

"Lighting People" want higher frequency AC, to totally eliminate incandescent light flicker (slightly noticeable at 25 Hz). 50 Hz solved the flicker problem, and the "Motor People" would grudgingly go with it.

"Clock People" wanted 60 Hz to make the design and manufacture of the numerous devices that had timing components easier (60 min/hr, 60 sec/min, 60 Cycles/Second).

Various electric equipment manufacturers "placed their bets" on which standard would "win".

The clincher was the development of a satisfactory large 60 Hz synchronous converter (A specially design rotating machine - sort of a "black box" for it's day - that turned AC into DC). This was not an easy thing to do until solid state electronics came along.

The synchronous converter allowed the "Motor People" to get their DC by joining the "Clock People" at 60 Hz. Also the "Lighting People" and nothing to lose (technically) by going from 50 Hz to 60 Hz.

And the rest is history.

I had a wonderful electrical engineering professor. He was in his mid-70's when I took his classes in the late 1960's. He had participated in, or had first hand contact with people directly involved in this type of "behind the scenes" work. He always enjoyed passing on this sort of info.

http://www.SlideRuleEra.net

 

[IRstuff]

All sounds reasonable, except for the bit about the clocks. There were almost no electronic clocks at the time the die was cast. Most clocks were geared, so there would have been no good reason to worry about dividing the line frequency evenly by 60

TTFN

 

[GregLocock]

And I doubt the regulation (or whatever you call it) of the supply frequency would have been accurate enough to use for timekeeping, at the time when the decision was made.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[ScottyUK]

Greg,

Actually it was! In the olden days, power generating stations would have two clocks. One was a precision chronometer, and the other was a mains-powered type driven by a synchronous motor. Over the course of the working day the mains clock would run slightly slow when the grid was heavily laden and the frequency dropped slightly, and during the night it would run slightly fast when the frequency was increased fractionally to compensate the slow period through the day. Over 24 hours the clocks matched each other.

Perhaps it was a cunning plan to lengthen the working day and reduce the time employees spent at home!

----------------------------------

I don't suffer from insanity. I enjoy it...

 

[SlideRuleEra]

Like ScottyUK says, the frequency varied (and still does) but the overall average was precise enough for everyday use. One application that our professor told us about where the hour-to-hour frequency deviations was a problem was radio broadcasting (1920's style). National Broadcasting Company (NBC) had all of there clocks on one circuit. Of course these clocks had synchronis motors, since electronic clocks did not exist - I believe the first commercial one was the Bulova "Accutron" watch which became available in 1960.

As one radio program ended (in one studio) the next program (in a different studio) had to start up at exactly the precise moment so that there was no dead-air time or overlap. With all the clocks on the same circuit - no matter what happened (power interuptions within the building, etc.) the clocks remained sychronized with each other.

If the frequency was too high - shut down the dedicated clock circuit until time caught up.

If the frequency was too low - switch the clock circuit over to a special generator in the building's basement that intentionally operated at an above normal frequency. Run the clocks at "high-speed" until they caught up with time. All the while, the clocks remain in sync with each other.

http://www.SlideRuleEra.net

 

[IRstuff]

Still unclear why 60Hz would be preferred over 50Hz for that. Since the clock motors were synchronous, and there's not yet been any mention of what one would need 1/60 of a second resolution for, and whether that would be sufficiently different than the resolution gotten from 1/50 second to matter.

As a shot in the dark, I'd be more tempted by the notion that the US didn't want to be running the same frequency that the Germans used, or something to that effect.

TTFN

 

[SlideRuleEra]

IRstuff - I have to agree that the "Clock People" being a major factor in the decision sounds odd, will see what I can find.

But in the meantime, here are some great pictures to go along with nate2003's original post

http://www.telechron.net/features/boulder.htm

http://www.SlideRuleEra.net

 

[Quantum50]

ScottyUK, that's what I've come to understand as well. As a matter of fact, I saw a program a couple of years ago that indicated the power companies still do that now for the purpose of correcting clocks among other reasons.

I wish someone from Europe with expert knowledge would comment on why Europe has remained at 50Hz and what problems come from it (clocks?) and the corrective actions.

 

[Quantum50]

Or rather, why is 50Hz preferable over 60Hz? My motors/transformer training is very rusty, sorry.

 

[GregLocock]

Thanks Scotty. So, when did the Europeans settle on 50 Hz? When did the USAns settle on 60 Hz?



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[IRstuff]

Some discussion here, for what it's worth:

http://en.wikipedia.org/wiki/Alternating_current#AC_power_supply_frequencies

http://answers.google.com/answers/threadview?id=505375

TTFN

 

[BJC]

I think people decided on 60 cycle because it's natural. ie, 60 seconds in a minute, 60 minutes in an hour. 360 degrees in a circle. etc. No big mystery they just though in 60s.

The cabel that brought the power to Los Angels was segmented copper. That is it was 8 or 10 strips that interlocked and sprialed around a spacer assemble. In the hot desert climate under load it creeped and got lower and lower. They changed it out just in time to use the copper in WW2 for bullets and shell.
In case you want to see it and buy a cool "Nerd TOy" the bur rec is selling them here.

http://www.usbr.gov/lc/hooverdam/service/memorabilia.html

 

[waross]

My understanding of the frequency choice is that the US originally started with 25Hz. When Europe started to electrify, they engineers realised that there were a lot of economies to be realised by using a higher frequency and used twice 25 hz. or 50 hz.
When the Us and Canada decided to change to a higher frequency, they took the attitude that if 50 Hz. was good, 60 hz. would be better.
I have had this understanding for so many years that I have no idea of the source of the information. It may be purely speculative.
As for the two clocks in the power house:
I understood that went out in North America many years ago when the utilities started to use time signals from the National Observatory to synchronize the generators on the nation wide grid.
BTW, I understand that Texas is an interesting exception to the inter-nationally interconnected power system.
respectfully

 

[notnats]

Motors and transformers are smaller and lighter on 60 hz, which is probably why it is pretty much standard on ships. I think aircraft use 300hz or similar for this reason

Jeff

 

[davidbeach]

Aircraft use 400Hz, not 300Hz. There are three independent grids in the US/Canada. The West is all WECC, most of Texas is ERCOT, and the East is a whole conglomeration of coordinating councils. All power transfers between the three grids takes place over DC links.