How is AC electricity made?? I may need BruceB for this one.

[mscher]

Re: How is AC electricity made?? I may need BruceB for this one.

"I guess more specifically I should have asked... where do the electrons come from? "

http://www.youtube.com/watch?v=R-Ma6iKLd7g&feature=related

Everything contains electrons.

It's the ability to move them, that determines what components are used where.

Electrons move rather freely in copper, so that why it's a good choice in electrics. Electrons barely move at all in ceramics (or most plactics, rubber), so that's why they make a good insulator.

The theory is that when electrons "move" in a compound, they leave a "hole" that will be filled by another electron, hence current "flow".

I'm sure it can be explained more complex than this.

 

[rodbolt]

Re: How is AC electricity made?? I may need BruceB for this one.

jlinder
thats about what I said in regaurds to power generation in most automobiles.
my 61 studebaker lark had a generator.
it also had headlights,tail lights,points,brake lights and an AM radio.
thats about the extent of the electrical load.
however if ya got stuck in the traffic jam in san rafel at the evening rush hour it was barely adequate.
my 70 cutlass convertable had an altenator with a seperate mechanical voltage regulator.
my 70 W-30 442 had the delco-tron altenator with the builtin solid state regulator.
the altenator was tried back in the 30's and 40's but using mechanical rectifiers and mechanical voltage regulators it wasnt practicle nor reliable.
kinda like disc brakes in the 30's.
they tried it, the technology did not match the theory.
now step up to my wifes 06 eddie baur bronco.
dang thing has heated seats,heated mirrors, sensors everywhere, Air conditioning and a rear window defrost.
stuck in the DC metro parking lot, also known as I-95, there is no way a generator would handle the load.
modern solid state electronics have come a long way since cars of the 50-60 and 1970 range.
had a 58 olds that the most sophisticated electronics were the clock, which NEVER worked right and the removable AM portable transistor radio which actually worked well but ate batterys.
plug it into the dash socket and it worked off the car battery and spaekers. unplug it and it used AA batteries and a built in speaker.

 

[jlinder]

Re: How is AC electricity made?? I may need BruceB for this one.

I know what you mean. In the 50s even the windshield wipers were not electric - they were driven off the vacuum from the engine. Now I have electric wipers, fog lamps, electric seat heaters, electric rear window defogger, electric side view mirror heaters, etc.

Don't want to think of what would happen to the battery with a generator and a good highway-5MPH-parking lot experience.

BTW -the 58 with the transistor radio was a step up. I remember tube radios. Dad would give us a ride to school in the morning (1.5 miles but the school district said we did not need busing but that is another story) and by the time the radio warmed up we were already at our destination.

 

[rodbolt]

Re: How is AC electricity made?? I may need BruceB for this one.

good old vacum wipers, my 57 GMC had them.
step on the gas to accelerate and the wipers would slow down or simply stop for a bit.
also had a foot operated manual starter pedal.
also had a non synchronized 3 speed on the tree.
was tricky to shift on a good day .

 

[jlinder]

Re: How is AC electricity made?? I may need BruceB for this one.

48 Chev. wipers ran off the dual action fuel pump. Opposite reaction. Pulled up to a light and the wipers almost stopped. If a good snow was falling it was enough to stop the wipers.

You had to give it some gas to clear the windshield before you could pull out.

Sorry we are digressing from the original topic, but it is Thanksgiving and time for nostalgia. That's my story and I am sticking with it

 

[j_martin]

Re: How is AC electricity made?? I may need BruceB for this one.

HAHAHA.
I still remember "some" of the stuff we took when it came to transmission and distrabution theory of power during lineman school, now I remember why I went telecom.
(only to come up against more and more different equations, IE wheatstone bridge SP)

J factors. Don't forget about J factors. aaarrrgggghhhhhh.

 

[rodbolt]

Re: How is AC electricity made?? I may need BruceB for this one.

kinda like radar and microwave generation,propagation,transmission and reception theory.
eyes glassed over and all you can do is hit the I belive button and wonder how come you cant get the same drugs that designer/theorist used.
mostly all I remember from 20 years ago is it seemed to work well .
\

 

[j_martin]

Re: How is AC electricity made?? I may need BruceB for this one.

kinda like radar and microwave generation,propagation,transmission and reception theory.
eyes glassed over and all you can do is hit the I belive button and wonder how come you cant get the same drugs that designer/theorist used.
mostly all I remember from 20 years ago is it seemed to work well .
\

Yea, the only way to explain a magnetron is majick.

 

[jonesg]

Re: How is AC electricity made?? I may need BruceB for this one.

Yea, the only way to explain a magnetron is majick.

Electrickery.!

 

[jlinder]

Re: How is AC electricity made?? I may need BruceB for this one.

Once you understand the magnetron take a shot at the TWT (Traveling Wave Tube)

Used mostly for satellite communications..

http://en.wikipedia.org/wiki/Traveling-wave_tube

 

[rodbolt]

Re: How is AC electricity made?? I may need BruceB for this one.

spent my first 3 years in the navy doing nothing but electronics schools, they kept saying do well in this one we will send ya to another.
I did, they did.
TWT is anchient technology, was in the late 80's.
but we had to learn it.
and yes I understand klystrons, tuneable klystrons, TWT's, magnatrons and the ocssilator circuits that feed them as well as wave guide propagation.
the cool things are the solid state amplifiers using tyristors and some other stuff.
cant comment on other stuff.
its actually what the US taxpayer trained me on, also why I post here.
just wish I remembered it now as well as I did then.
and yes we trained in ELF,ULF VLF,VHF,UHF,micro wave and FLIER.
as an FC in the USN our job was to start fires.
hopefully on someone elses real estate.
my most basic schools
BE/E top of my class.
FC(A) top of my class
CIWS (C) school, top of my class.
I joined the USN for an education at age 27, I actually took it serious.
had a wife,spent my 7th wedding anniversary at RTC great lakes.
daughter turned 3 7 weeks before I hit RTC great lakes.
so yes I was trained well, simply dont get to use it much now.

 

[levittownnick]

Re: How is AC electricity made?? I may need BruceB for this one.

Wanna repeat all that?

 

[bruceb58]

Re: How is AC electricity made?? I may need BruceB for this one.

However, when you are talking about moving huge amounts of power long distance they use DC. The main power grids in the US and other countries use DC to move the power long distances then convert back to AC for local distribution.
http://en.wikipedia.org/wiki/Electric_power_transmission

I am not a power engineer but have never heard of HVDC being used in the US.

 

[rodbolt]

Re: How is AC electricity made?? I may need BruceB for this one.

when moving electrons at a high voltage or a high frequency or better yet a high voltage AND frequency, most the rules you learned in auto shop cease to exist.
amplidyne theory and maint is nuts as is wave guide and wave propagation theory and maint.
sometimes ya simply gotta toggle the I belive switch.
electricity is simply smoke and PFM sometimes.
keep the smoke in and the rest is pure freaking magic.

 

[jlinder]

Re: How is AC electricity made?? I may need BruceB for this one.

I am not a power engineer but have never heard of HVDC being used in the US.

You would not be exposed to the DC distribution unless you worked on the national power grid. The country is divided into 4 grid sections from east to west. Inside these grids the power is distributed as AC, however, between the grids the power is shared as DC.

Try the original link for a start, then look at this for HVDC in the US. http://en.wikipedia.org/wiki/Eastern_Interconnection

 

[jlinder]

Re: How is AC electricity made?? I may need BruceB for this one.

........
TWT is anchient technology, was in the late 80's.
but we had to learn it.
and yes I understand klystrons, tuneable klystrons, TWT's, magnatrons and the ocssilator circuits that feed them as well as wave guide propagation.
the cool things are the solid state amplifiers using tyristors and some other stuff.
cant comment on other stuff.
........

While the TWT is ancient it is still in use.

SSPA (solid state power amplifiers) are getting better and higher in power, and with digital transmission we can work with lower power, but there are limits.

The SSPAs tend to hit their practical limits at around 100w or so at the high frequencies (think KU - around 12GHz). If you are just transmitting data or audio you can typically do it with that power. But go into the world where you can be transmitting multiple videos signals via one transponder and you need a good bit more power. The SSPAs are just not up to the task just yet.

 

[waterinthefuel]

Re: How is AC electricity made?? I may need BruceB for this one.

rodbolt -

The move from DC generators to AC alternators had more to do with the availability of reliable solid state diodes to convert the AC back to DC than anything else.

Generators have a problem in that the voltage is proportional to the speed of the generator, which is dependent on the speed of the engine. At idle the generator does not create enough voltage to put any charge into the battery. That is why the headlights on the older cars would dim somewhat when idling.

Alternators on the other hand can be designed to have the voltage peak exceed the voltage of the battery. Peak - not the average. This means that at idle the alternator still puts out some current to the battery.

If you had an engine that ran at a constant RPM you would be better off with a generator.

A great example of this is a helicopter. (I used to do some flying in a Bell Jet Ranger). Helicopters run with a constant RPM for the rotor (at least this one did). They use a generator instead of an alternator.

Interesting side note is the same generator serves as the starter motor. They use it to get the jet engine up to speed (at least enough to get it to light and run), turn it off for 60 seconds to let it cool down (takes a long time to spin the jet up to speed), then use it as a generator to charge the electrical system.

And that part is known as a starter-generator and is an amazing piece of equipment. They use them in helis not because of the constant rotor RPM but because of space and weight requirements.

 

[jlinder]

Re: How is AC electricity made?? I may need BruceB for this one.

And that part is known as a starter-generator and is an amazing piece of equipment. They use them in helis not because of the constant rotor RPM but because of space and weight requirements.

Agreed about the space-weight requirement and that is why they use a combined system. My point was that the constant RPM makes this possible.
(well maybe you don't need a constant RPM, but you can count on the engine not dropping to idle speeds as you would in an automobile)

 

[Tim Wagner]

Re: How is AC electricity made?? I may need BruceB for this one.

Electricity is smoke.
the bigger the wire, the more smoke.
ever notice when something roasts, all the smoke?
Once all the smoke is left out the thing quits working.

Couldnt reisist this one!

 

[dockwrecker]

Re: How is AC electricity made?? I may need BruceB for this one.

I had no idea we had so many electrical geeks here...