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After finally getting all your arrangements for time travel together, you've landed in the 1880s, just as the battle between Tesla and Edison is starting to begin. For reason, $reason$, and reason you need Edison to win this thing. Unfortunately, Edison's system has some major disadvantages from the beginning that will ultimately lead to its downfall. For one, the lower voltages used by DC transmission results in higher cable prices, where as AC can utilize transformers to step up electricity to much higher voltages for transmission, and many preferred the cheaper alternative.

After a bit of convincing you get Edison to accept the solution of high voltage transmission, provided you can build him a transformer. However, being from the future, you know that DC transformers are absolutely possible. Transistors allow the production of boost converters for stepping up DC voltage and buck converters for stepping it down. Unfortunately, in the 1880s the transistor was a long way away, and the simplest vacuum tube, the diode, wasn't created until 1904. As such, you need to find a way of building Edison a DC-DC transformer in the 1880s.

Other problems:
- All solutions must be achievable with 1880s technology and knowledge. In this circumstance transistors wouldn't be feasible, as the theory for them was not yet established and the technology to produce them was not yet produced. Having Edison "invent" the vacuum tube may be viable, but you must suggest a way to produce them in the 1880s.
- Killing Tesla or sabotaging his operation is not allowed.
- Copper prices were rising during this period, so cheaper is better.

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    $\begingroup$ You want us to build a DC voltage converter with late 19th century technology, and have it be feasible and economical? Is that even possible, given the constraints? $\endgroup$ – BMF Mar 10 at 3:17
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    $\begingroup$ At the moment of late 1800, the utilities were mainly local (town,city). As such, the price of copper needed to rise absolutely 2-3 orders of magnitude, and even then I reckon using higher (than 110V) voltages with iron wires would have been a solution - thicker and heavier, but then they wouldn't be hard pressed by long distances. It is only when the utilities reached the 'national' level that the losses over long distances became an issue. $\endgroup$ – Adrian Colomitchi Mar 10 at 4:30
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    $\begingroup$ When I read the title of the question, the first thing that flashed through my mind was "Edison's Conquest of Mars" gutenberg.org/files/19141/19141-h/19141-h.htm. The actual question seems to be about as feasible as an electric airship... $\endgroup$ – Thucydides Mar 10 at 4:36
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    $\begingroup$ Welcome to NYC. First blood! An elephant has been slained by Edison, assist Tesla. JP Morgan is nearly out of minions. $\endgroup$ – user6760 Mar 10 at 4:56
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Dynamotor, and you're done.

You can make DC transformers. You just have to spin them.

Now, you will get into some commutation issues as you push the voltage higher. You can make the commutator larger and larger (although increasing commutator wear as you do, since the linear speed is the wear issue). But you can probably get about 5000 volts out of this.

Beyond that, you'll have to be a bit more extreme. One option is to run the commutator in an oil bath instead of open air. However, the fast motion will tend to cause cavitation, so you'll need to pressurize the oil vessel. This will add drag, and will still have limitations, so there's an idea:

Throw a bone to Tesla. Stay in the AC regime for high voltage distribution. Really, generate on AC, then use a rotary converter to convert AC for DC distribution. Now you can use simple slip-rings on the AC side.

But don't rest your laurels there, work on 3-phase AC distribution, and then work to use mercury arc rectifiers for the AC-DC conversion.

Split-pole service for double the voltage

Suppose you want to distribute 110 VDC to homes. (you've had a couple bumps from 100V DC to increase distribution capacity). Actually, distribute a 110/220V split: +110V, common, and -110V. It's one more wire, but this allows you to connect larger draw appliances as 220V for more efficient distribution, yet have the safer 110V for smaller loads.

If the 110V loads are reasonably balanced, then you have two opposing poles putting roughly equal current on the "common" wire. Those currents cancel each other out, leaving little current on the common wire, and thus, negating their voltage drops.

No, I didn't get that idea from anywhere. Why do you ask?

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Having Edison "invent" the vacuum tube may be viable, but you must suggest a way to produce them in the 1880s

Edison is the inventor of the electric bulb - except with a carbon filament.

You will need:

  1. convince him to declare an armistice with Tesla and push the tungsten filament ahead of time

  2. use the so discovered/applied technology, and invent the vacuum tubes. Essentially, he already almost done it (it was discovered before him, he rediscovered the thermionic emission in his bulbs, but wasted himself in his war with Tesla instead of continuing the research).

  3. let Tesla win the AC/DC wars - because Tesla worth winning - and use the vacuum tubes to take the voice-over-radio transmission from under the nose of Marconi and Landell de Moura - on short waves, using 1-10W power - rubishing in the process not only the spark-gap early radio, but Graham Bell and his telephone too.

  4. continue with the applications of thermionic emission and 'cathod rays' and invent the CRT display. Coupled with the radio, get the TV before the end of 19th century.
    Oh, boy, can you imagine the power of advertising on TV? Betcha the great depression of the '30-ies would have been avoided! (:grin:)


Notes

Transistors allow the production of boost converters for stepping up DC voltage and buck converters for stepping it down.

  1. both of boost/buck converters work essentially on AC - this is why Tesla worth winning the war

  2. TANSTAAFL - the losses in DC-DC converters grow beyond what AC/AC transformers can do at the same Vin/Vout ratio. Granted, capacitive losses on the (very) long lines in AC are a thing too - but outside a national grid (only local utilities) these are not significant.

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