Some History on Electricity

[Chuckt]

George Westinghouse

https://en.wikipedia.org/wiki/George_Westinghouse


War of Currents

https://en.wikipedia.org/wiki/War_of_Currents

This fills in some history.

[Garth]

Those are very interesting, but I only scanned them quickly, because of the length.

DC is obviously not practical, and Edison was apparently only thinking of light bulbs and motors, not planning ahead to vacuum tubes that would require hundreds of volts for their plates, or solid-state equipment that would later require 12V, 5V, 3.3V, 2.5, 1.8V, or even less, or for the need for isolation. Now we have switching regulators to efficiently kick DC voltages up and down; but the huge capacitors that would require for megawatt applications, and the huge amount of electrical noise they would make, kind of puts them off limits for much of what transformers do with such ease, efficiency, dependability, and long life. Before switching regulators, DC voltages could be kicked up with dynamotors, ie, motor-generators, but their efficiency was poor, and they had limited lifetimes.

When I was in school, a teacher was telling us that 60Hz is the most dangerous frequency for the heart, and that you could get killed on as little as 60V; and joked that here in the U.S., when they chose our line voltage and frequency, they picked the worst frequency, and then doubled the voltage, just to make sure.

In the country I grew up in, they used 220V, 50Hz. I suppose the 50Hz was a compromise between wasting less power by transmitting it into space on long runs, and the required increased size of transformers. The higher voltage was undoubtedly chosen because it was not as rich a nation, and the higher voltage allows using much smaller wire, using less copper. Safety standards were not as good though, and also buildings used a lot of concrete and very little wood. Floors were typically polished concrete tiles over a concrete slab. Concrete is never really dry, so if you stand on a floor bare-footed, or in socks or similar footwear that's moist from your feet, you are well grounded! Now reach up into a lampshade to turn on the lamp and inadvertently find something that's not well insulated, and the plug is plugged in in reverse (since there was no protection from that), and wow, it was painful! It would grab you hard, and it might be very difficult to let go! Or, you might use an appliance that had a transformer in it, and there's capacitive coupling between windings, and even though there's no DC path, you might get bit, although not as hard. Turning the plug over would usually fix the problem.

[brad]

I thought it may have been a war between conventional and electron current flow.

There is a high voltage DC submarine cable between the Australian mainland and Tasmania:

https://en.wikipedia.org/wiki/Basslink