US system is not as inefficient as I once thought

I read in sci.engr.electrical.compliance that Matt wrote (in ) about 'US system is not as inefficient as I once thought', on Tue, 30 Sep 2003:

Tesla and Yagi were there before you!

Reply to
John Woodgate
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Yes, though not normally appliances for domestic use. Refrigeration compressors with motors above around

2kW would likely be 3-phase.
Reply to
Andrew Gabriel

Europeans already have this.

Robert

Reply to
Robert Calvert

I think you are at least partly right about this. Large aircraft typically use 400 Hz because this frequency allows for the use of smaller and lighter motors and transformers. I don't know what this does to energy efficiency but, on an aircraft, I suppose that size and weight are the most important considerations.

Robert

Reply to
Robert Calvert

Interesting. I wonder if anyone can give a similar explanation for the

25 Hz systems which I understand were generated in Niagara Falls, and even New York City prior to the introduction of 60 Hz. I've even met the odd, older, individual who remembered the changeover so it's not really all that ancient.

Dave

Reply to
Dave Holford

Right, assuming the balanced condition your electrician described. But between the breaker box and the devices using power, higher voltage results in less I^2*R loss in the wires for the same wattage devices.

Reply to
ehsjr

The early subways used DC because of the ease of varying the speed by varying the voltage. Alas, DC isn't so convenient to distribute, so they distributed AC and converted it to DC using synchronous rotary converters (this was before the mercury arc rectifier).

If nothing else is changed, a 25Hz synchronous rotary converter spins slower that a 60Hz. synchronous rotary converter, and these were big machines which were difficult to design to run at the faster speeds. One could add additional poles to bring the speed down, this meant more commutator segments , which, if the size was kept the same, would be packed closer together and thus have higher voltage gradients, risking increased arcing. Make them bigger and you increase the surface speed at the commutator, which wears it out faster. There is a picture of one of the commutaors at

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- as you can see, it was already quite large.

There is a lot of good material on this subject at

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Reply to
Guy Macon

double negitive . . I DO NOT FOLLOW MANY OF THESE NEWS GROUPS To answere me address mail to snipped-for-privacy@aol.com

Reply to
BUSHBADEE

I believe that, at least at the time of Tesla etc. lower frequencies were _more_ efficient for motors and transformers, not less. 50/60 Hz was a compromise between efficient low frequencies and lamp flicker. Note that electric railroads, trolleys and subways often used frequencies such as 20 Hz, 25 Hz or even 16 2/3 Hz (Europe). The Niagara Falls hydroelectric facility generated 20 Hz at first. (I beleieve it was even available until maybe 20 years ago on the Canadian side) Amtrak between NYC and Philadelphia _still_ uses 20 Hz.

Related question: What other "weird" frequencies were/are used? In addition to the above, I saw an 1898 GE generator in an old wool mill rated at 40 Hz, and planes use 400 Hz (presumably for lighter transformers and generators)

Reply to
Michael Moroney

What double negative?

Reply to
ehsjr

The U.S. Rural Electrification Administration (REA) had as much to do with selecting single phase - 3 wire - 110/220 volts 60 Hz to be the U.S. Standard as much as anything during the 1930's when farms were being electrified during the Great Depression.

Existing electrical installations were considered (including the European 220 v - 3 phase systems).

The U.S engineers at the time determined that the 3 phase systems could be simplified to single phase 3 wire 110/220 volt which would allow electric motors of up to 10 HP to be used for farm chores, pumping water, etc. (Any AC motor greater than 10 HP is out-of-necessity going to be a 3 phase motor) (Interestingly enough, many AC motors at the 10 hp threshold were of the repulsion start induction run type). Bottom line, the resulting simplification in equipment (one single phase transformer serving perhaps one or two isolated farmhouses with a primary ground return was determined to be the most efficient system. The lower of the two secondary voltages available 110/220 v. was deemed to be important for safety reasons (and compatible with existing US standards). Although 3 phase was desirable, it wasn't considered absolutely necessary for most residential and farm needs that could utilize up to 10 hp motors.

There was much discussion in this newsgroup recently of SWER (Single Wire Earth Return) systems. Presumably, this was not considered in the U.S. due to both safety considerations and the resulting interference that strong ground return currents would have caused to telephone and (in those times) telegraph circuits.

Beachcomber

Reply to
Beachcomber

I think he in trying to say that "not as inefficient" is a double negative, but that rule properly relates to absolute as opposed to relative phrases. "not non-efficient" would be a double negative, but I do not believe that "not as inefficient" is.

A college professor taught "double negatives are used in some dialects to express strong negative, but logically, a double negative is a positive. A double positive, however, is never used to express a negative." A voice from the back of the class replied "Yeah, Yeah..."

Reply to
Guy Macon

Except that earlier systems were almost exclusively delta-connected primaries with two conductors running down roads where 3 phase was not available. The electric poles had a crossmember at the top with insulators supporting a single wire at each end.

Single conductor with ground return didn't seem to become common until the 60s.

Reply to
Michael Moroney

The way I heard it was the voice said, "Yeah, Right...." (think of it in a sarcastic tone that would imply not agreeing i.e. a 'negative' formed by a double positive)

daestrom

Reply to
daestrom

And depending on what part of the world you're talking about, it isn't 'common' even today. Many rural areas around NY have what I think are wye connected phase running down the country road. One phase on insulators, one grounded neutral that is run above. Grounded neutral high-line seems to serve double duty as a lightning guard wire. Can at pole connected across them on primary, and three-wire output to house/barn.

daestrom

Reply to
daestrom

I believe there is still a 16 2/3 Hz supply system for train or trams in Europe... and they recently changed to 16.7Hz to get away form harmonics of 50Hz (another supply frequency) ...

Reply to
Frank Warner

| daestrom wrote: |> Macon wrote: |> ehsjr wrote: |>>> BUSHBADEE wrote: |>>> double negitive |>> What double negative?

| > I think he in trying to say that "not as inefficient" is a double | > negative, but that rule properly relates to absolute as opposed to | > relative phrases. "not non-efficient" would be a double negative, | > but I do not believe that "not as inefficient" is.

| > A college professor taught "double negatives are used in some | > dialects to express strong negative, but logically, a double | > negative is a positive. A double positive, however, is never | > used to express a negative." A voice from the back of the | > class replied "Yeah, Yeah..." | >

| | The way I heard it was the voice said, "Yeah, Right...." (think of it in a | sarcastic tone that would imply not agreeing i.e. a 'negative' formed by a | double positive)

Your college professor was right. However, double negatives are used is MOST dialetcs to express strong or stronger negatives.

Consider the following:

Macon, I need some money. Do ya have any?

No.

No, hell no.

No, I ain't got any.

No, I ain't got no money.

no, I ain't got no money, no way.

No, I ain't got no money, no way, no how, no time.

no-no-no-no, I ain't got no ...

All mean the same thing. You ain't getting any money. _________________Gerard S.

Reply to
GerardS

non-efficient = not efficien. The as makes a comparitive statement. . . I DO NOT FOLLOW MANY OF THESE NEWS GROUPS To answere me address mail to snipped-for-privacy@aol.com

Reply to
BUSHBADEE

On Thu, 02 Oct 2003 10:20:50 +0000, Guy Macon Gave us:

Excellent response, yeah, yeah.

Reminds me of a Phil Collins song.

Reply to
DarkMatter

No, it is 400volts, not 460volts in three phase areas. A second phase is used for installations above 60 amps or so. It may be 230/460volts in rural areas with single phase HT.

Reply to
Peter

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