[I suppose this is more a kind of human rumination on the Trinity more than a parable. There’s actually no way one can completely explain the concept of the Trinity. But the doctrine of the Trinity is the only way to make sense of many statements in both the Old and New Testaments.]

Andrew: Hi, what are you up to today?

Alex: I’m trying to sort out this Sprague connection.

Andrew: Oh, is that what one calls this funny plug?

Alex: No, it’s the whole thing.

Andrew: But why’s that plug got 4 pins and not the usual 3?

Alex: 3 lives (i.e. 3 phases) and one neutral; the earth is via the metal casing and this open copper wire.

Andrew: So which is positive and which is negative?

Alex: No, no: it’s AC – alternating current, each live is both positive and negative; it alternates.

Andrew: Oh, I thought alternating current was when we alternate between we’ve got current, we’ve got blackouts; you know, Es-kom, Es-gaan.

Alex: No, the current flows first one way, then the other. It rises to a peak, drops, reverses, becomes negative. Look, let me draw you the graph of AC. I’ll just scribble here.

Copy of Single phase Sine_wave_2.svg

This is what we call a sine wave. You can see where its positive peak (say forwards) is , and where its negative (when it goes backwards) peak is. The whole cycle is 360 degrees; that’s what the figures at the bottom are. In South Africa it does this 50 times per second!

Andrew: Good grief! And this three-phase business?

Alex: OK; what I drew there is single phase. I’ll draw you a 3-phase diagram now. It will look a bit more complicated, because we have 3 phases in one diagram. So I’ll do it in colour if you have a red pen …. Thanks.

 Andrew: I can’t believe it does that 50 times per second; and now you say there are 3 of these; so that’s 150 times per second?
Alex: Not quite. Look here’s the diagram.

3PhasePowerWaveF

You must realise this is ONE current supply in 3 phases; or 3 phases in ONE current supply. Let’s say that above the horizontal “0” line is positive, and below is negative, but remember, it’s the same current in the same cable. We could number the phases, but it’s better to draw them or their wires in different colours. You’ll notice the phases are staggered; we say the second one is 120 degrees later compared to the first, and the third is another 120 degrees later than the second, like your mom’s melktart divided into 3 equal pieces and the angle in the middle is 120 degrees. Four equal pieces would have made it 90 degrees.

Andrew: But don’t they get muddled? The phases, I mean, not the melktert.

Alex: No; they’re in separate wires; that’s why I said there are 3 lives. So you have 3 distinct phases, each with its own “function” (shall we say) but they work together in a kind of unity. They work simultaneously; so there’s never a time when there’s only two or one phase operating. You see they never cross on the horizontal line marked “0″ simultaneously.

Andrew: Okaaaay … But what about the 4th wire?

Alex: Right. That’s the neutral. When those three phases in the lives are completely balanced, there should be no current in the neutral. That’s the theory anyway; so don’t think you can play with it, because in practice it may well have some voltage. The earth, of course, is a connection from the chassis of the motor to ground. So, if there’s voltage on the chassis (which there shouldn’t be) it can leak to earth rather than shocking you. Then you’d be buried in a different kind of earth, hey?

Andrew: Wow, this is so complicated. I mean, it goes backward and forward. The same wire is positive and negative; and there are 3 phases and one current supply and they all exist simultaneously?

Alex: Ja, that’s about it. Each phase has its separate existence and can be measured separately; but they work together in a kind of unity as one current. In fact if you measure the voltage from one phase to neutral, you’ll get 220 volts (assuming Eskom is working!). If you measure “across the phases” you’re going to get about 380 volts.

Andrew: Complicated.

Alex: Not if you study the field. Remember when you tried to explain the concept of the Trinity to me? It just didn’t make any sense. I mean, surely God is one, but you say, “No: three persons in one God. God is the Father; God is the Son; but the Father isn’t the Son; and the Spirit isn’t the Son but ‘proceeds from the Father and the Son’, ‘Filio quoque’,” and all that. Now I just didn’t get that. I mean Jesus was only in existence for some 33 or was it 36 years. But you said, “No, He’s been in existence all the time.” And you also claimed Jesus was both divine and human. Now that didn’t make sense either; just like you don’t get it that AC has both pos and neg in the same wire. I mean, that’s just the way electricity works.

Andrew: It’s certainly difficult for the layman to grasp.

Alex: And shall I tell you something else?

Andrew: What?

Alex: How does electricity flow; I mean, in which direction?

Andrew: You mean, like, from positive to negative?

Alex: Exactly. Now what is electricity? What is it that actually moves?

Andrew: OK, so I know that: we were taught it’s electrons.

Alex: Right. So in which directions do electrons flow?

Andrew: Obviously from positive to negative.

Alex: So you’d think; but actually electrons go from negative to positive.

Andrew: But that’s a contradiction. It can’t be right!

Alex: And yet the theory and mathematics of it all work.

Andrew: No, can’t be.

Alex: So are you an unbeliever? Let me tell you, this IS the way it works. You theological guys aren’t the only ones to have crazy-sounding ideas, which you say are not really crazy, but just too deep.

Andrew: Ja, but, I mean, this is supposed to be science!

Alex: So? “There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy.” That’s from Willem Wisselstroom’s play Hamlet, by the way.

 

Graphs from:
http://en.wikipedia.org/wiki/File:Sine_wave_2.svg
http://en.wikipedia.org/wiki/Alternating_current

7 November 2014

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