Mains transformer weights

Significantly? No... One for 400 Hz would however.

About 20%. Is that significant?

not really a lot of difference.. ~ 17% lighter. But you must remember that many places where 50Hz is used, the voltages are a little different so one transformer could conceivably be used for both. It most likely wouldn't pass a local ordinance rule due to a name plate not agreeing.

For example, not to long ago I approved a motor to be used in a 480 60hz application where the name plate was as a ~400 v 50hz unit. End results was the same, with the exception of a little higher RPM than marked on the ID of course.

Just think V/hz ratio.

Jamie

It is also not uncommon for smaller power transformers to be rated as

Following on from this, why is it that electricity generation is limited to such low frequencies as 50 or 60 Hz ? As the frequency rises, the energy lost through electromagnetic radiation from the wires rises, but is it really a significant amount ? Would it be significant at 1 kHz ? If not, why isn't generation done at that sort of frequency ? The savings in transformer weights and sizes everywhere would be enormous. Is it because of mechanical engineering limitations on the rotational speeds of the large rotary generators the power stations use ?

Losses. Mechanics.

Yes.

Yes, certainly.

Partly. 1kHz translates to a 60,000 RPM generator. That's kinda high for a generator of a useful size (60Hz = 3600RPM, much better). Multipole generators are possible, but that only reduces this linearly and increases the size similarly.

Instead of hum, you would have whine.

Good point. Perhaps it should be 20kHz. ;-)

Hmmm, waveguide at 133kv. Sounds like that would qualify for an energy department grant.

Jim Hawkins schrieb:

Hello,

Bye

Like a lot of Usenet posts. ;-)

Ha. I have a sticker on my helmet that says "Stop Global Whining". :)

Regards, etc.

"Jim Hawkins" wrote in news: snipped-for-privacy@supernews.com:

I have worked in the airforce, they also used 400 Hz on(or under) the ground. You could hear the 3rth harmonic(1200 Hz) all over the place, wich is not such a good idea in your home. Very iritating for new workers, old workers had a measurable dip in their hearing curve, and could not hear that frequency anymore.Permanent damage.

Huh? Where does anyone say 1kHz translates to a 60K RPM? The speed and frequency are not related, the speed and the number of poles in a generator head determine the frequency. Most 400 Hz generator sets run at 2000 RPM. Your flawed concept would have them running at 24K RPM!

the

Now you've gone and done it! Very few people remember that Alexanderson Alternators were used as very early keyed transmitters, when 'Spark was king!' They have never seen anything like Alexanderson's designs, and the concept isn't covered in any book on motors I've ever seen. I learned about them, years ago while studying early radio.

Read the link:

Not *my* concept.

Goes back to about 1903. about a dozen or so installed worldwide. Most decommissioned before and during WWII.

There's one in Sweden that still gets run up, once a year.

What is a generator "head", BTW?

OK, not your idea, sorry I implied that. (Or said it, as the matter may be!)

A generator head is the part that makes the electricity, and is (typically) attached to an engine or other motivating device (water wheel or turbine).

Never heard it called that before. To me, the electrodynamic part is a generator, the whole installation is a "generating set".

Maybe it's power-station-speak.