It makes me sad that only that TINY area is light-blue.
Lots of area with the correct voltage, but a stupid frequency.
Other areas with low voltage, but the right frequency.
and the brown areas that are as wrong as possible. lol.
Historically, here in the States, 117VAC was chosen for residential power because that was deemed the highest voltage that isn't usually quite lethal (doesn't that make you all warm and fuzzy?). And I've been told that 60 cycles was chosen because the flickering it causes in arc-lamp sources (which were the most common electrical light sources back then) is just fast enough that it's not visible to adults (apparently kids can see it -- their eyes are just a bit faster to respond). The flickering is actually at TWICE line frequency since the arc intensifies at voltage maxima, both positive and negative.
In reality, the voltage/lethality curve is just that, a curve. Higher voltages are more likely to be lethal, you can pick your point on the curve. It's also true that high voltage delivers power at a lower current than lower voltage, requiring less copper (smaller wires), so there is a good reason to favor higher voltage when you can.
Higher frequencies do have some advantages. Light flicker became a non-issue with incandescent light bulbs, but it reappeared with fluorescent lighting. I remember even at 60 cycles I could see the flickering when I was in high school; close fluorescent lighting could give me a migraine. As far as efficiency goes, the fact that 360 is evenly divisible by 60 is a meaningless numerical coincidence, but it is true that a transformer designed for 50 cycles will have to be somewhat larger than the equivalent transformer designed for 60 cycles...the magnetic coupling that a transformer uses is more effective at higher frequencies. That's why airplanes distribute power at 400 cycles -- it makes for much smaller transformers, saving weight, which is critical on airplanes. But there are other considerations as well. Motors become difficult to manufacture at too high of a frequency, and the larger the motor, the more difficult it gets. Also, power lines actually radiate some power away, like radio frequency antennas, and the higher the frequency, the worse the power loss becomes. Skin effect can become a factor on very large conductors, and is worse at higher frequencies.
As is almost always the case, there is no "good" power and no "bad" power. There are only design compromises that have to be made.
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Topic: EV@TucsonEV.com (Read 3583 times)