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#128273 - 01/03/03 02:30 AM Why 50 or 60 Hz
FAHardy Offline
Junior Member

Registered: 01/03/03
Posts: 2
Why is the supply frequency 60 Hz (or 50Hz in the UK) and not a lower or higher frequency. Are there any applications where a higher generating frequency is used

#128274 - 01/03/03 06:23 AM Re: Why 50 or 60 Hz
sabrown Offline

Registered: 12/12/02
Posts: 297
Loc: Ogden, Utah, USA
Why back then, I assume that it was natural to use 1/60 of a second because we have 60 minutes in an hour and 60 seconds in a minute. And I assume 100 half cycles also seemed like a logical number to use for those who decided on the foriegn systems.

There are economic advantages to both.

60 Hz gives a maximum speed of 3600 rpm versus 3000 rpm for 50 Hz. Also large distribution transformers have material savings up to 10-15% due to better flux linkage of the higher frequency.

50 Hz does transmit over long distances slightly better because of less inductive reactance.

To use a mixed 50/60 Hz system makes no economic sense because the advantage for such small gains is lost in conversion.

Are other frequencies in use? Yes.

We have large high voltage DC transmission over long distances.

Variable frequency drives allow speeds greater than 3600 rpm by using higher frequencies.

Airplanes AC systems are most generally 300 Hz.

300 Hz also was prevelant power provided for some computers.

#128275 - 01/03/03 07:47 AM Re: Why 50 or 60 Hz
wolfdog Offline

Registered: 10/24/01
Posts: 135
Loc: Dallas,TX
Hey sabrown, I thought aircraft was 400 Hz.
Have I been mis-informed?

#128276 - 01/03/03 01:31 PM Re: Why 50 or 60 Hz
pauluk Offline

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
The 50 and 60Hz standards probably evolved as a convenient compromise between the various conflicting factors.

They're certainly not the only distribution frequencies used in the past. The 50Hz used in the U.K. became a national standard only in the 1920s.

Lower frequencies have been common for electric railroad operation, including 25Hz and 16-2/3Hz. Some such systems are still operating in some counteies.

I've always associated 400Hz with aircraft, but I've also seen it used in watercraft. Some of the cross-Channel and Irish Sea ferries operating out of the U.K. have 400Hz electrical generation, with suitable warnings for travelers using equipment which might be frequency sensitive.

One of the main advantages to using a higher frequency such as this is the reduction in the size and bulk of transformers. That's why the switched-mode power supplies found in almost all modern TVs and computers change the incoming supply to a much higher frequency (typically 15kHz or more) before applying it to a xfmr.

#128277 - 01/03/03 02:42 PM Re: Why 50 or 60 Hz
sabrown Offline

Registered: 12/12/02
Posts: 297
Loc: Ogden, Utah, USA
Oops on the 300, I may have also remembered the computers incorrectly in that reguard.

#128278 - 01/05/03 05:25 AM Re: Why 50 or 60 Hz
Scott35 Offline

Broom Pusher and

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
Too low of Hz, and rotating machinery is effected by slow speeds + Lighting will have distinctive pulsations.

Low Hz also requires larger core /coil setups for Inductive machines (Induction Motors, Transformers, Ballasts, etc.)

Higher Hz causes Induction Motors to have a higher fundamental rotating speed, plus core/coil sizes are reduced.

The downfalls:

Lower Hz - Lower Xc but increase Xl, Larger core/coil designs but lower Skin Effect;

Higher Hz - Lower Xl but increase Xc, smaller core/coil design but increased Skin Effect.

50/60 Hz is something that was a "Happy Medium" between George Westinghouse's equipment builders and Tesla's Engineering specs. From what I remember, Tesla wanted to run around 100 Hz, or higher - but was "forced" to Engineer the equipment's specs for 60 Hz.
50 Hz is not too different from 60 Hz, but both are way off the scale when viewed by 400 Hz.

BTW: Fluorescent Lamps are much "happier" when they are driven with High Frequency AC, as opposed to driven by 60 Hz AC!
Drive them at 40 KHz instead of 60 Hz and they will "Smile"!!!

Scott s.e.t.
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

#128279 - 01/05/03 02:06 PM Re: Why 50 or 60 Hz
C-H Offline


Registered: 09/17/02
Posts: 1508
Loc: Stockholm, Sweden
I might add a few lines: At the turn of the century (you know which ) other frequencies were indeed in use. (I've seen figures from 25 to 144Hz) Lower frequencies made motors smaller/simpler, higher made the transformers smaller. (This was before high precision manufacturing and ball bearings.) Just like the others have said, 50/60Hz was (and probably is) a good compromise. The 50Hz on one side of the Atlantic and 60Hz on the other arise from two different companies being dominant: In North America it was Westinghouse while in Europe it was AEG. (Germany pretty much dominated Europe industrially prior to WWII.)

#128280 - 01/05/03 04:49 PM Re: Why 50 or 60 Hz
Bjarney Offline

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
The history of 25Hz in Northeastern US industrial districts is oft discussed, but there was another “standard” frequency in another US region. Until 1936, what is now Los Angeles Department of Water and Power operated at 50 Hz. There is an account in the IEEE Power Engineering Review about the change intricacies for AC-powered clocks in the area. At that point frequency went up to 60Hz, but even today the area uses the classically "Euro" voltages of 220-, 110- and 33kV in their system.

Crookshank & Kinsler, 1936 Los Angeles Synchronous Clock Project June 1997 IEEE-PER

#128281 - 01/05/03 07:36 PM Re: Why 50 or 60 Hz
pauluk Offline

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
Fascinating -- I never realized that anywhere in the U.S. ever used 50Hz as a standard.

Japan still has both 50 and 60Hz in different districts. So far as I'm aware, they are the only country to still have multiple frequencies for normal distribution (i.e. ignoring special system, railroads, etc.).

I've often thought that the frequency must be quite a problem for those in the Carribean who "island-hop" on a regular basis.

#128282 - 03/23/03 05:07 PM Re: Why 50 or 60 Hz
ZackDitner Offline

Registered: 10/11/02
Posts: 46
Loc: Kitchener, Ontario, Canada
It's my understanding that until the 50's, ontario was still supplied with 25Hz power, i remember old timers telling me that you could see a light bulb flicker if you looked carefully enough.. Then we decided to share power back and forth at the niagara power plants with the us, and went to 60hz in order to be able to easily sell power back and forth. The first generating stations at niagara got converted to 25hz AC from DC i believe. Could be wrong here..


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