Electrical Engineering - Higher or lower frequency AC

Author

Higher or lower frequency AC

Hunter

2007-05-12, 3:25 am

Hi,

I'm an amateur hobbiest in electrical science. Could anybody please show me
an internet link or some basic reference explaining the mechanics on how 60
hertz household AC supply can be transformed into something higher or lower,
lets say from 10 hertz to 1000 hertz?

Why is 60 hertz standard in the US? Any special advantage compared to the 50
hertz in Europe?

Thanks.

Palindrome

2007-05-12, 3:25 am

Hunter wrote:
> Hi,
>
> I'm an amateur hobbiest in electrical science. Could anybody please show me
> an internet link or some basic reference explaining the mechanics on how 60
> hertz household AC supply can be transformed into something higher or lower,
> lets say from 10 hertz to 1000 hertz?
>
> Why is 60 hertz standard in the US? Any special advantage compared to the 50
> hertz in Europe?
>
There are two basic ways of converting electrical power from one
frequency to another -

1) Electro-mechanical, using a motor running at one frequency linked to
a generator running at the other

2) Electronic, typically converting the energy to dc and then converting
the dc to the new frequency.

You possibly already have something that will convert 60Hz (or 50 Hz)
input power to output power at any frequency from 10 -1000 Hz. It's
called an audio amplifier. You just need to provide a low power signal
generator of the required frequency as its input, plus, perhaps, a
transformer at the output to produce "mains" voltage. A suitable
amplifier will produce several hundred watts of output power at the
desired frequency.

As to why the difference in frequency. Personally, I put it down to the
arguments that a different frequency should be adopted outweighed those
that the same frequency should be used. eg If you want to establish a
new industry in a country and don't want to be swamped by imports from
an established industry elsewhere - you adopt a different and
incompatable standard..

http://answers.google.com/answers/threadview?id=110766

Beachcomber

2007-05-12, 5:25 pm

>As to why the difference in frequency. Personally, I put it down to the
>arguments that a different frequency should be adopted outweighed those
>that the same frequency should be used. eg If you want to establish a
>new industry in a country and don't want to be swamped by imports from
>an established industry elsewhere - you adopt a different and
>incompatable standard..
>

This question comes up in this thread periodically.

In brief, electrical systems evolved into the standards we used today
during the early years of the 20th century. Going back to the late
19th century, there was the DC central station, and limited power
distribuiton to a few city blocks at low (110 V) voltatages (in the
USA). Then came the AC systems of Tesla and Westinghouse, which
allowed for long distance power transmission and interconnection of
large generators at distant points.

In the early years of the US Electrical Industry, there were many
different frequencies available 16 Hz, 20 Hz 25 Hz, even 40 Hz in
addition to 50 and 60 Hz systems. In general, the lower frequencies
were better for operating large electric motors (elevators, hoists,
streetcars, and railroad locomotives) due to the lower inductive
reactance.

Incandescent lighting became popular on these same systems, but at the
low frequencies (50 Hz and below), there was a noticable flicker in
the low wattage lamps.

Gradual interconnection and the development of network grids all but
eliminated the oddball frequencies and 60 Hz was chosen to be the
default frequency in the North American System along with a voltage of
110V and later, the split-phase 110V/220V system that is still used
today. The voltage and frequency chosen was a compromise to take the
best characteristics of the systems at the time and make them a
regional standard.

Electric System Development in Europe was dominated by the Siemens AG
who made many of the generators and whose engineers picked 50 Hz as
the standard for Europe, with most distribution at 220V, and 3 phase
as a standard.

No one at the time envisoned universal appliances, hair dryers,
washing machines, computers, tv's, entertainment electronics, etc that
could be used in any country. It was not a problem for many years
until travellers started pluging their110V. electric shavers or hair
dryers into 220V outlets and blowing them up.

Now we have universal power supplies and UPS sytems that put out
either 50 or 60 Hz power at various voltages.

phil-news-nospam@ipal.net

2007-05-13, 3:25 am

On Sat, 12 May 2007 22:08:10 GMT Beachcomber <invalid@notreal.none> wrote:

| Gradual interconnection and the development of network grids all but
| eliminated the oddball frequencies and 60 Hz was chosen to be the
| default frequency in the North American System along with a voltage of
| 110V and later, the split-phase 110V/220V system that is still used
| today. The voltage and frequency chosen was a compromise to take the
| best characteristics of the systems at the time and make them a
| regional standard.

It was split "phase" 110/220 as early as Edison's DC service in New York
(though one would call it split polarity to be more correct).

| Electric System Development in Europe was dominated by the Siemens AG
| who made many of the generators and whose engineers picked 50 Hz as
| the standard for Europe, with most distribution at 220V, and 3 phase
| as a standard.

As I understand it, they chose 50 instead of 60 because it fit better
with the metric system. But I have no idea if this is true.

| No one at the time envisoned universal appliances, hair dryers,
| washing machines, computers, tv's, entertainment electronics, etc that
| could be used in any country. It was not a problem for many years
| until travellers started pluging their110V. electric shavers or hair
| dryers into 220V outlets and blowing them up.

Or plugging their 220V shavers into 110V outlets and watching them overheat
and burn up.

| Now we have universal power supplies and UPS sytems that put out
| either 50 or 60 Hz power at various voltages.

I'm still looking for a decent UPS that can do 240V 60Hz using the split
phase wiring of North America. And surge protectors for it would be nice
to have, too.

--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2007-05-12-2338@ipal.net |
|------------------------------------/-------------------------------------|

contrex

2007-05-13, 9:25 am

On 13 May, 05:42, phil-news-nos...@ipal.net wrote:

> As I understand it, they chose 50 instead of 60 because it fit better
> with the metric system. But I have no idea if this is true.
>

I thought it was because it made synchronous machines run at 3000 rpm,
which is a nice round number.

phil-news-nospam@ipal.net

2007-05-13, 9:25 am

On 13 May 2007 01:56:10 -0700 contrex <mike.j.harvey@gmail.com> wrote:
| On 13 May, 05:42, phil-news-nos...@ipal.net wrote:
|
|> As I understand it, they chose 50 instead of 60 because it fit better
|> with the metric system. But I have no idea if this is true.
|>
|
| I thought it was because it made synchronous machines run at 3000 rpm,
| which is a nice round number.

For that they should have either changed the clocks to have 50 or 100
minutes per hour, perhaps with 10 or 20 hours per day, or just used a
frequency of 16.666667 Hz to get a nice round 1000 rpm (oh wait ... they
actually did that for a while). OK, how about a nice round 50 rps?

--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2007-05-13-0914@ipal.net |
|------------------------------------/-------------------------------------|

contrex

2007-05-13, 1:25 pm

On 13 May, 15:17, phil-news-nos...@ipal.net wrote:

> a frequency of 16.666667 Hz to get a nice round 1000 rpm (oh wait ... they
> actually did that for a while).

They still do for traction on Scandinavian, German, Austrian and Swiss
railways. It used to be 16 2/3 Hz (ie 16.6666 recurring) in all those
countries but some have changed to 16.67 for technical reasons.

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