The abbreviation Hz” refers to the physicist Heinrich Rudolf Hertz, who became famous by the discovery of faster electromagnetic waves. In some countries especially in US and Canada 60Hz is applied. That means, an AC motor rotates with a ratio 60/50 = 1.2 times faster, which is 20% faster than the 50 Hz main frequency. The genesis of the standard 60 Hz frequency began during the well known war of currents between George Westinghouse/Nico Tesla and Thomas Edison. In contrast the history of 50-Hz lies largely in the dark and still waiting for to be exposed.

The German company AEG (descended from a company founded by Edison in Germany) built the first German generating facility to run at 50 Hz, allegedly because 60 was not a preferred number. AEG’s choice of 50 Hz is thought by some to relate to a more “metric-friendly” number than 60. At the time, AEG had a virtual monopoly and their standard spread to the rest of Europe. After observing flicker of lamps operated by the 40 Hz power transmitted by the Lauffen-Frankfurt link in 1891, AEG raised their standard frequency to 50 Hz in 1891.

After observing flicker of lamps operated by the 40Hz power transmitted by the Lauffen-Frankfurt link in 1891, AEG raised their standard frequency to 50 Hz in 1891.

In the mid-1890s of Europe there was an increase of preference for the period number of 50. A timereport highlighted the advantage of the quick and easy procurement of engines, arc lamps and partly of transformers”, which were produced by a large number of factories.

Westinghouse Electric decided to standardize on a lower frequency to permit operation of both electric lighting and induction motors on the same generating system. Although 50 Hz was suitable for both, in 1890 Westinghouse considered that existing arc-lighting equipment operated slightly better on 60 Hz, and so that frequency was chosen. Frequencies much below 50 Hz gave noticeable flicker of arc or incandescent lighting. The operation of Tesla’s induction motor required a lower frequency than the 133 Hz common for lighting systems in 1890. In 1893 General Electric Corporation, which was affiliated with AEG in Germany, built a generating project at Mill Creek, California using 50 Hz, but changed to 60 Hz a year later to maintain market share with the Westinghouse standard.

In the early days of electrification, so many frequencies were used that no one value prevailed(London in 1918 had 10 different frequencies). As the 20th century continued, more power was produced at 60 Hz (North America) or 50 Hz (Europe and most of Asia). Standardization allowed international trade in electrical equipment. Much later, the use of standard frequencies allowed interconnection of power grids. It wasn’t until after World War II with the advent of affordable electrical consumer goods that more uniform standards were enacted. In Britain, a standard frequency of 50 Hz was declared as early as 1904, but significant development continued at other frequencies. The implementation of the National Grid starting in 1926 compelled the standardization of frequencies among the many interconnected electrical service providers. The 50 Hz standard was completely established only after World War II.

By about 1900, European manufacturers had mostly standardized on 50 Hz for new installations. The German VDE in the first standard for electrical machines and transformers in 1902 recommended 25 Hz and 50 Hz as standard frequencies. VDE did not see much application of 25 Hz, and dropped it from the 1914 edition of the standard. Remnant installations at other frequencies persisted until well after the Second World War. Now in current European Union the frequency is 50Hz throughout (and the voltage within the EU have been adjusted to attain an average of 230V +/- 10% in all countries.

In resumee, the use of 50 versus 60 Hz is purely due to historical reasons, with companies in the US making 60 Hz equipment and those in Europe making 50 Hz equipment so that they have a monopoly. This rivalry led to the split you see today.

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