On Oct 30, 7:33 am, David Billington
wrote:
bob wrote:
On Oct 30, 4:01 pm, Randy wrote:

This group seems to have alot of electrical knowledge, sooo.....

The US is 60 HZ and Europe is 50 HZ, a 60HZ motor is more efficient,
so, what would happen if the US or the world for that matter would
switch to 120 HZ or maybe even as high as 400HZ (which is common in
aircraft). Motors and transformers would be much more efficient,
power savings could be enormous, both in transmission and use.

I realize this would have to be a 50 to 100 year task. Laws would
need to be passed and electronic devices would need to be sold that
would work on both frequencies. (many switching power supplies such as
in computers do not care what freq. power is input.)

I've read a bunch of articles about the newer inverter type welding
power sources that use 400 HZ and use small transformers and use much
less input power for the same output power.

I'm guessing it would take a panel of "experts" a few years to work
out the costs VS savings for this one. I've heard of some really
stupid things being studied by our government, maybe someone should
look into this.

I bought some old machinery from the Bethlehem Steel plant that was 25
cycle, WOW, talk about inefficient!! I had a 5hp motor that was built
on a 15 hp frame size.

Ideas, thoughts??

Biggest problem I think would be the generating end of things.

Thank You,
Randy

Remove 333 from email address to reply.

I think that you are mixing up size and efficency. The higher the
frequency the size for a certain power output decreases. But ! the
losses from eddy currents and the like increase. There is a crossover
point which was below 50 hz in the old days ....most of the old
generating stations were 25 hz and even 16 2/3 Hz.
Today with modern steels and thinner laminations the cross over point
is much higher. But that is not the only point to consider ! with high
voltage transmission lines the losses climb with frequency and
distance. The very big long ones even use DC !

Interesting you mention DC transmission lines. My neighbours were in
China last year and saw the new big dam, they were told the generating
station produced 500kV AC for local use and 500kV DC for long distance
transmission. Subsequently I have been told that some UK electricity is
supplied by France as DC. My question is what sort of gear is used to
convert the DC to AC. A big motor generator unit?.



Regards Bob

Perhaps I can answer the question about the DC transmission of power.

The Dalles dam on the Columbia river transmits power to the LA area
using DC. In the late 1970's, I think, I was in the Portland Amature
Radio club. A member was an engineer for a local power company. He set
up tours for us to several interesting power generating facilities,
and one was the DC converter station at the Dalles dam. The station
takes 18 phase AC power, yes, 18 phase, at several thousand volts. The
power is then fed into several rows of mercury vapour controlled
rectifiers. They stand on ceramic insulators about 10 feet above the
floor. The output of the rectifiers feed power at 250,000 volts over a
pair of wires all the way to LA. The origional plan was to use both
lines at 500,000 volts and use the earth as a return. Law suits
stopped that because of the havoc caused by the ground currents.

An identical installation is on the LA side of the transmission lines.
There the controlled rectifiers convert the DC back to AC. The system
is symetrical in that when the river flow is low in the winter and the
people in LA are not using their air conditioners, the excess power is
sent back to the Northwest using the same AC to DC system.

The entire transmission system is controlled by computers. Even back
in the 1970's.

A very interesting and educational experience.

Paul