20-Jul-2000 (Thu)

I figured out how to update the metadata in the audio streams, so you can now see the title of the current song, if your MP3 player supports that.

The reason we were offline for about an hour today is that Covad dropped a bunch of their SF customers for some unknown reason. Our connectivity has not been super-reliable, and my ISP and Covad keep pointing their fingers back and forth at each other. Me, I'm betting on it being Covad's fault, but really I just wish the problem was even understood.

Our electrician stopped by today to meet with the PG&E rep, and while he was here, I had him give me a remedial lesson on electrical power distribution. He was very tolerant of my ignorance, I can tell he likes his job! So this whole electricity thing, it all seems very ad hoc, really. I get the impression that the background on a lot of this stuff is, ``this is how Nicola Tesla did it, so we're still doing it that way now.''

The Eminently Skippable ``Ask Dr. Science'' Interlude:

    So down at the power station, they have these generators. Heat runs turbines, and turbines turn a big magnetic wheel. Around the magnet are three sets of coiled wire, evenly spaced 120 degrees apart. As the positive pole of the spinning magnet swings by one of those sets of coils, its field induces a positive (or negative? I forget) current in that coil, and as the negative pole swings by, it induces the opposite current. One end of the wires in each of these three coils is attached to the planet (``ground''), and the other end leaves the building. Inducing a current means that the magnetic field sucks a whole bunch of electrons up out of the earth and pushes them through the wire, then lets them slide back the other way. That's AC, ``alternating current.''

    So the reason that there's any talk of ``three phase power'' at all is because that's how the electric utilities actually make it: the generators have three sets of coils on them. Maybe there's some efficiency reason for this, or maybe it's ``just because.''

    The ``phase'' part comes from the fact that the three lines have voltage curves that are out of phase with each other. If you were to graph the voltage of one of the output wires over time, it would go from +120 to -120 and back again, each time the magnet spins around (60 times a second in this country.) But the starting point of each of these sine waves are offset by 1/3 of the cycle.

    So then there are two types of transformers that this power might go through before it reaches you. The internal details of these things are kind of neat, and made my brain dredge up things I haven't had to think about since my high school trig class (study math, kids! It's useful for more than writing video games!) but the bottom line is, the output of one type of transformers is two 120 volt lines, and one 208 volt line; and the output of the other type of transformer is three 120 volt lines.

    The first kind is called a ``delta'' transformer (because schematically, it's a triangle) and the second kind is called a ``star'' or ``three-phase'' transformer. The difference between them is just how the three hot lines are wired together. I'd explain how that works, but to do that I'd have to draw pictures of them, and I'm just not up to that right now. I'll give you a hint, though, and it's that 208 is 120 times the square root of 3.

    Anyway, ``delta'' transformers are what feed your house, because all of the stuff you own runs on ``single phase'' 120v power. It turns out that there's pretty much nothing in the world that uses 208v power, so that third leg on a delta transformer is useless.

    Things like residential clothes dryers run on 240v, which is a pair of 120v lines strapped together. Though ``240'' is sometimes spelled ``220'' and ``120'' is sometimes spelled ``110'' for some reason. Taxes? Inflation?

    Big electric motors like to run on ``three-phase'' power, because they can feed each of their three sets of coils from a different power source, and they're already properly out of phase with each other, so that's very efficient. (Remember, motors and generators are the same device, one's just running backwards.) So big gear such as compressors and walk-in refrigerators tend to take three-phase power.

    Well, this neighborhood only has delta power. This seems odd to me, since this used to be a warehouse and industrial district before all the yuppies moved in, and I would have expected there to have been a lot of heavy equipment here, but apparently not.

So anyway.

What we've got in here is 400 amps of delta, meaning a pair of 120v lines and a single useless 208v line. The electrician ran his numbers again, cut some things out, and was able to come up with a plan for our equipment that shows us using only 366 amps. So that means that we can run this club with the the sound and light system that we're getting, and still have power to spare, without having to upgrade the service. We'll be pretty close to maxed out, and if we want to expand, like if some day we want to put in a real kitchen, we'll need to upgrade the power then.

So imagine that! We are able to operate a nightclub on the amount of power on which a nightclub has been operating here for decades! I for one am shocked. Shocked, I say.

The PG&E rep thinks (she's going to check) that we actually have 600 amps available to us, if we dig up four feet of the sidewalk and run some new feeds. The electrician seems excited to do this, but it's not clear to me that it's necessary. It's also not clear to me how much doing this would cost, but I'm guessing, oh, let's say, a whole hell of a lot. I anticipate this being one of those situations where someone wants me to replace something because it's ``old'' or ``beige'' or ``just plain needs killin','' then I'm going to say ``but does it work?'' and they're going to say, ``...well... yeah'' and I'm going to say ``so what's the problem?'' and they're going to say ``well... nothing, I guess.''

I have this kind of conversation a lot. It's very frustrating.