Kilo-Whats? Or, advancing toward less ignorance

Trains Magazine General Discussion
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It is high time I started learning more about how electricity works. I really had no training of it in school; even physics was theoretical. Thus far in my life I’ve learned that AC and DC radically differ (from a movie about the N.Tesla/T.Edison conflict) but am not quite sure how; that a “T and D” (transmission and distribution) is a local (deregulated) utility that doens’t generate its own power, and how to divide watts by volts to get amps (and even then, the air-conditioner is too much for the circuit!).

I’m not out to get a B.S.E.E., but I’d love to know what people mean (say, on this site) when they write things like “The [new electric motor locomotive’s] points blasted so easily the trainsets spent half the time in the barns.” (OK, I do understand the second half of that sentence); but what would happen if one of Chicago’s bi-level (aluminum-roofed) Metra Electric trainsets tangled with catenary wire? My father blew out a perfectly good electric razor when he plugged it into a DC circuit in a Manhattan apartment building in the Forties, before I was born; nevertheless, Dad knew a lot more than I know, like why (or how) cheap box fans go OFF-3-2-1 instead of the other way. He explained it once but I didn’t grasp the concept. OFF 1-2-3 just seems more logical in an intuitive way.

As much as I love the GG-1, I confess I have only a very basic understanding of how it worked, or why 750 Kv DC could power such a huge thing. I can’t read a schematic. For all kinds of reasons I just didn’t pick up “the basics” to a point where it looks as though I have no “common sense” at all.

Here are a few book Amazon readers have recommended. If you have any comment toward any of theses, or have your own to recommend, I would really appreciate your taki

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Al –

I’m not certain how “deep” you want to go.

So – while a book may do the trick for ye, and I’m sure you’ll get some wonderful recommendations, why not start HERE and HERE and click into some of the links.

I use infosites like these all the time. It’s amazing sometimes how much you can learn at these places, and they may be more up-to-date than a book – and far cheaper. Often, I can get lost for hours on Wikipedia, just clicking through one topic’s links to another related topic’s links. Wikipedia has some great basic historical info and links for railroad history on particular railroads, especially fallen flags.

PZ

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PZ’s sites are a good place to start. Don’t feel bad if you don’t grasp everything right away, though. I have worked for journeymen electricians that couldn’t explain how electricity works if their lives depended on it. I have apprentices that are in the same boat now.

It can be a difficult thing to get, but with a little math and a lot of ‘hands on’ experience it will eventually make sense. E-mail me if you got questions.

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Remember that it usually took four years or so for us old folks to get that old BSEE degree, so don’t expect to grasp things overnight. You need to read and get a “feel” for how things work; how much math you want to apply depends on how deep into the workings of electron pushing you want to get. Surprisingly, it is harder for a lot of people to get the “feel” than it is to get the math, based on some of the engineers I worked with in my checkered career.

OK, just for the record, “hands on” here is a figure of speech; taking that too literally can be a little more than painful.

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Middleton’s When the Steam Railroads Electrified has a good primer on what makes electric locomotives tick, touching on DC vs AC, catenary vs third rail, etc. He doesn’t get too heavy into electrical theory, so you don’t need to have a BSEE to understand it. A good background in electrical theory, spefically electrical machinery, does do wonders in understanding the why of different approaches.

A couple of real simple formulas to keep in mind, POWER=VOLTSxAMPS, and for voltage drop across a resistor VOLTS=CURRENTxRESISTANCE.

One other thing to keep in mind is that motors motor control systems have evolved enourmously since the dawn of RR electrification. The first trolley cars used simple rheostat controls with DC series motors (i.e. starting with high resistance in series with the motor(s) and gradually switching out the resistance - this where ‘points’ come in). Next step was series-parallel switching. The next step was the invention of the interpole which allowed for high-voltage DC operation (1200V for interurban service in 1907, 2400V for the BA&P in 1913 and 3000V for the CM&StP in 1916). The DC series motors were a decent fit for RR operation, having the highest torque at low speeds, but also having disadvantages of being relatively expensive to make, relatively fragile commutators and esentially two speed operation for most locomotives (full series or parallel). The points on the control system were subject to wear (although the contactors on locomotives were a bit more rugged). The series resistors were only to be used for starting the car or train and overheated badly if engaged too long (the museum at Rio Vista Junction lost a car when the controller was left on a resistance point for too long).

Chopper controls were developed in the 1960’s, which allowed for continuously variable speed control. Another advantage was potentially greater life of the control system as the need for mechanical switches was mostly eliminated (they

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Just to pick up on a couple of your questions, Al…

Probably the first thing to get rather firmly in mind – rather than worrying too much about AC and DC and 3 phase and all (all of which is horribly important, but not right now!) is the distinction between volts (as in 750 kv DC which you mention – which isn’t right, by the way, the GG1 ran on 11 kv single phase AC), amps (like a 20 amp circuit breaker in your basement) and power.

Volts may be likened most easily in visual terms to pressure in a pipe. All by itself, volts wont do anything (your cat can easily generate several thousand volts with one pat). But it can, and does ‘push’.

Amps may be likened to flow. The more amps, the greater the flow.

Now… power is the ability to do work. And power, very very roughly, is the result of a pressure (volts) causing a flow (amps) across a resistance of some kind. One can visualise that if there is a resistance, but no volts, there will be nothing to push the electricity around and no flow and no power. If there is a flow, but nothing for it to push against, there is no need for any pressure, but again there is no power. So on a very fundamental level, power (watts) is the product of volts (pressure) and amps (flow).

Now before the BSEEs get mad, let me remind you all that I’m a Civil E, not and EE… but I do know the differences between volt-ampers and watts, and something about power factors, and all that…

In DC electricity, the current is always flowing in the same direction. There are some advantages in this. There are also some very major disadvantages. In AC electricity, the current reverses direction at regular intervals – usually 25, 50, or 60 times per second (but 400 in aircraft work). There are some advantages in this, too, as well as some disadvantages. The biggest single advantage to AC is that one can easily change the voltage with a transformer – a gadget which, in its si

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You picked up on that, huh? It has been my experience that the quickest way to learn about electricity is to get shocked by it - keep in mind I don’t advocate this but I had some journeymen that told me you are going to get nailed by it at some point so you might as well experience it while we’re around to help you. You do learn mighty quick what is a safe work practice and what isn’t. Today I can work safely on live circuits up to 480V with bare hands. This is a dying skill, however, as OSHA mandates that all electricity be de-energized before working on it. Or you have to put on the snowsuit. Younger folk are not being taught this skill, and I believe they are not as safe because of it.

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In my wasted youth, I got bit a few times, HV DC more often than AC, which I liked less. It was a lot easier after I did my EE, but then I went back into integration labs and had to get my hands dirty, or at least stand close to a tech doing the dirty work.

There is nothing like a good jolt or a vaporized screwdriver shank to increase your respect for electrical energy and maybe make you work a little safer.

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Or that scar on the back of my hand from a -105DC contact, or that set of dikes that became a wire stripper over a 110VAC cord that wasn’t unplugged?

You’ve got some excellent advice and knowledge here. Don’t cast too wide a net - some basics of electricity and their application on railroads will do just fine. The minutae can come later - like how a DC locomotive transitions between series, series-parallel, and parallel…

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I’m a BSEE also (actually a BSE - the EE come later). But I have spent my career in milli watts rather than kilo watts.

milli = 1/1000ths of a watt

kilo = 1000 watts

there is a difference.

dd

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This is great, guys, keep it comin’! - a.s.