Definition: The mains frequency is the frequency of the electrical energy supply in an AC-based power grid and is expressed in Hertz.
In Europe, Asia and Australia, most of Africa and parts of South America, a general power frequency of 50 Hertz is used. In North America, on the other hand, 60 Hertz is common. This difference is historically determined: When the first power grids were created at the end of the 19th century, a dispute arose between advocates of alternating voltage and advocates of direct voltage. On the other hand, different technological bases in America and Europe led to the establishment of different frequencies in the field of alternating voltage: 60 Hertz in America and 50 Hertz in Europe. These differences still exist today, although there are no technical reasons for them. For historical reasons, different network frequencies are still used in Japan today: 50 Hertz in the eastern part, which was supplied with generators from Germany in 1895, 60 Hertz in the western part, where generators were supplied from the USA.
Standardization or conversion to direct current is not seen as profitable in the short term, which is why global differences remain.
Due to the historical differences in grid frequencies, components of industrial plants have to fit the local conditions. Most equipment suppliers offer components for both mains frequencies.
Different mains frequencies are used worldwide.