Where did AC v come from?

The earliest commercial alternating current frequency was 60Hz and the voltage was 110 V. Its inventor Nikola Tesla was an American (immigrant) and funded by the boss of Westinghouse Electric, commercial AC power is also the first operation in the United States. The US uses the imperial unit, and the 60Hz/110v specification is used for calculation convenience.

After the success of the commercial alternating current (AC) Competition, Europe quickly introduced exchange power generation and feed technologies. In Europe, all metric units except the UK are used. For calculation convenience, the frequency is changed to 50Hz. After V power supply
Low pressure and high transmission loss of the power grid. To improve this situation, the voltage specifications of V are adopted in European countries without large-scale construction of the AC power grid and thus there is no "burden, this is from V,
The technical transformation is relatively simple, so a 220 V/50Hz AC power grid standard has been formed in European countries.

After 1949, China's industrialization fully switched to the Soviet model. The construction of power grids also followed the Soviet standard, while the Soviet Union adopted European standards. Therefore, 220 V/50Hz was finally set as China's power grid standard.