Evolution Of Alternating Current Power In The U.s.

[atunguyd]

USB type C is now rated at 100w per port so this would be a viable option for in wall sockets as a DC power source.

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[John Hasler]

At 20V that's 5A per outlet, and you still need wire for your 120VAC high power devices. Little 100W switchers are cheaper than copper wire.

 

[Dabbler]

On the DC front, we have a 500 mile HVDC transmission line here. it cost 3 times what an AC line of the same capacity would have cost. It was done not for technological reasons, but for political ones. One day HVDC lines will be cost competitive.

 

[whitmore]

Edison may get his revenge. They are getting the preliminary legal stuff done to build a multi state DC power line by me. Grain Belt Express. Public meetings etc. I think they told me 1 million vdc. Feasabillity? Contrary to what I was taught.

Ah, but it's economic now (and wasn't back in the olde days). What makes AC so special
is that it can be transformed so easily; but as a consequence AC powerlines lose power
to the dirt-and-rocks-and-mud-and-stuff in the vicinity, which transform AC power
into heat. Once you start up an electric grid (circa 1935, "rural electrification") and
run long power lines (hundreds of miles) the DC advantage for long distance power
transmission becomes very interesting.

Edison didn't have hardware to convert AC to DC and back, efficiently. We do.

 

[markba633csi]

Where are all the cool fuel-cell cars I used to see in Popular Science? With the aluminum-air batteries- just drop in
a stack of plates and GO!

 

[cathead]

All the new technology such as TVs and computers are powered with switching mode power supplies(SMPS). They are
not designed to last since some of the parts have a finite life, notably the electrolytic capacitors. This makes for huge
amounts of electronic scrap piling up in various places of the earth as these units fail. The old style transformer power
supplies were much more dependable and repairable as well, much heavier though. One advantage of a transformer
power supply is that it does not generate any radio frequency(RF) interference like the SMPS supplies do. Almost
every house has a bunch of small "wall wart" units(generally SMPS) which have the potential to cause interference
in the RF region. It's not on one frequency either as they generate a base frequency as well as a bunch of harmonic
frequencies too. We are not immune to these problems as hobby machinists either. Variable frequency drives(VFD) are
basically a switching power supply too containing a number of electrolytic capacitors just waiting to fail. I have a VFD
and I like it today but I know that some day in the future it will ultimately fail. A lot of electronic equipment is not recycled
properly which is pretty sad. We wear our horse blinders and enjoy our modern electronics at the expense of our environment.

Sorry to be on a rant but I have been repairing several old SMPS units and realize that all that glitters is not gold.
If I can keep my own units from gravitating to the scrap pile, so much the better. I'm on a big learning curve trying
to figure out how to repair them so forward progress is being made.

I'm including a photo so that we are all at least aware of the environmental impact.

 

[markba633csi]

So true Cat, the e-waste problem is enormous, as well as the plastic in the ocean