AC v/s DC


Adam Cline wrote this excellent book, The Current War, on the fight to decide whether AC (alternating current) or DC (direct current) would be the electrical standard. As the book says, it wasn’t a fight based on just the technical aspects; it was also a clash between two titans and their companies.

It all began when Thomas Alva Edison invented the light bulb. But there was no wiring to get electricity into people’s homes. And so:
“Edison would need more than the light bulb. He would need to come up with a whole new industry (to supply electricity).”
Edison created an electric utility company based on DC (direct current). But transmitting DC power over long distances wasn’t possible due to the energy loss along the way. So end users had to be located within one-mile of the power generating plant. Thus, Edison and DC were restricted to the congested cities.

George Westinghouse, another businessman, had heard of AC (alternating current). It could be stepped up to high voltages before transmission, and then stepped down to voltages safe for customer use. The advantage? Stepping up allowed for power to be transmitted long distances. Westinghouse went with this approach and targeted sparsely populated rural areas. Then he went after the cities by “selling electricity at a loss”, thereby gaining even urban market share! It was game on between Edison v/s Westinghouse, DC v/s AC.

If AC can be transmitted far but DC can’t, why did Edison go with DC? Understanding AC needs a whole lot of physics and maths, but Edison had no formal education. Plus, he thought that others were trying AC only because he owned most of the DC side patents. And his bulbs worked easily with DC.

But AC was proving to be the superior option on every practical parameter:
1)      It had lower power losses than DC transmission;
2)     Lower power losses in turn allowed for thinner copper wires, which lowered the cost compared to DC which needed thicker wires;
3)     It could be transmitted much farther than DC;
4)     AC energy was easier to generate;
5)     AC machines were easier to operate and maintain.

Nikola Tesla was a very smart inventor who worked for Edison. When he presented his seemingly futuristic ideas about AC to Edison, they were brushed aside as being impractical. Later, the two had a falling out over money. Embittered, Telsa quit and formed his own company. He designed and patented an AC induction motor that eliminated sparking problems and lowered maintenance costs. Westinghouse heard of it, bought Telsa’s patents, and gave him a royalty on sales. Tesla’s technical capabilities were tilting the scales.

Since AC was proving the superior option, Edison switched to the only weapon he had remaining: fear and propaganda. Like all propaganda, it had its share of real facts, exaggerations and lies. High voltages of AC transmission could be fatal, hardly what you wanted near your homes, argued Edison. He cited real and fictitious incidents where people got electrocuted and even died.

Hearing of deaths by electrocution, the government thought of using high voltage AC as a way to execute prisoners instead of hanging them. Edison was elated: AC-can-kill was exactly the kind of publicity he wanted! Westinghouse was horrified for the same reason. The PR side of the fight was in full swing.

In 1893, Chicago had won the rights to host the World Fair. And the city was keen to use it as a platform to gain national recognition. Part of their strategy was to use electricity for lighting, something still not very common. Strangely, Westinghouse didn’t even bid! A small local company bid and won and asked Westinghouse to be their contractor. Edison had bid and lost; and he was furious. He heard that Westinghouse was going to use his bulbs for lighting and sued. And won. Edison’s bulbs could not be used for the Fair. Westinghouse scampered to design a new bulb of their own. Edison sued for copyright infringement, but this time he lost. Finally, when the Chicago World Fair was lit up, it became the first large scale test of the AC system. Not only was it successful, it had succeeded on a very visible platform, both nationally and internationally.

AC had won.

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