Re: slight subject change DC AC transmission lines?



kfvorwerk@xxxxxxxxx wrote:
On Oct 30, 3:17 am, bob <b...@xxxxxxxxxxx> wrote:

On Oct 30, 4:01 pm, Randy <rbraun...@xxxxxxxxx> 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,


I seem to remember reading that Westinghouse-Tesla AC was chosen over
Edison DC because the AC could be transmitted with lower power loss
over distance. So was AC more efficent at the distances it was being
transmitted at the begining of the electrical revolution?


Yes, because there WAS the AC transformer. You could use a DC-DC
motor-generator set, but there are practical limits to how much voltage you can get out of a generator armature. It was pretty easy to see that with no moving parts, you could get much better insulation in a transformer, and thus transmit power at kilovolt levels with existing technology in the late 1890's.

With Edison's DC system, you couldn't convert voltages without rotary machines, and nobody was going to have a 1000 V line feeding a rotary converter in their basement. And, nobody wanted 1000 V on their bulbs and light switches. So, if the entire system ran on 120 V DC, then you had large currents flowing all through the system, and got pretty big voltage drops in just a couple city blocks. You could fight this with big wire on the poles for a while, but it soon got out of hand.

The pole transformer outside my house runs on 7200 V, so it is a 30:1
winding (primary to the full 240 V secondary). So, if I am pulling the full rated load for my house (200 A) the transformer is pulling 6.67 A from the high voltage distribution mains. MUCH easier to send 6.67 A down a wire than 200.

Jon

.

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