ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Increasing demand factors in residential
by gfretwell - 03/28/24 12:43 AM
Portable generator question
by Steve Miller - 03/19/24 08:50 PM
Do we need grounding?
by NORCAL - 03/19/24 05:11 PM
240V only in a home and NEC?
by dsk - 03/19/24 06:33 AM
Cordless Tools: The Obvious Question
by renosteinke - 03/14/24 08:05 PM
New in the Gallery:
This is a new one
This is a new one
by timmp, September 24
Few pics I found
Few pics I found
by timmp, August 15
Who's Online Now
1 members (Scott35), 271 guests, and 12 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
#128273 01/03/03 06:30 AM
Joined: Jan 2003
Posts: 2
F
FAHardy Offline OP
Junior Member
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

Stay up to Code with the Latest NEC:


>> 2023 NEC & Related Reference & Exam Prep
2023 NEC & Related Reference & Study Guides

Pass Your Exam the FIRST TIME with the Latest NEC & Exam Prep

>> 2020 NEC & Related Reference & Study Guides
 

#128274 01/03/03 10:23 AM
Joined: Dec 2002
Posts: 337
S
Member
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 11:47 AM
Joined: Oct 2001
Posts: 135
W
Member
Hey sabrown, I thought aircraft was 400 Hz.
Have I been mis-informed?

#128276 01/03/03 05:31 PM
Joined: Aug 2001
Posts: 7,520
P
Member
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 06:42 PM
Joined: Dec 2002
Posts: 337
S
Member
Oops on the 300, I may have also remembered the computers incorrectly in that reguard.

#128278 01/05/03 09:25 AM
Joined: Oct 2000
Posts: 2,723
Likes: 1
Broom Pusher and
Member
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"!!! [Linked Image]

Scott s.e.t.


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
#128279 01/05/03 06:06 PM
Joined: Sep 2002
Posts: 1,498
Likes: 1
C
C-H Offline
Member
I might add a few lines: At the turn of the century (you know which [Linked Image] ) 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 08:49 PM
Joined: Apr 2002
Posts: 2,527
B
Moderator
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 11:36 PM
Joined: Aug 2001
Posts: 7,520
P
Member
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 09:07 PM
Joined: Oct 2002
Posts: 47
Z
Member
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..


Link Copied to Clipboard
Powered by UBB.threads™ PHP Forum Software 7.7.5