The choice of frequency is not as obvious as one might think at first glance. Between 1885 and 1900 there was a range of frequencies in use in the United States: 140, 133 1/3, 125, 83 1/3, 66 2/3, 60, 50, 40, 33 1/3, 30, 25 and 16 2/3 Hz. Each frequency had its own scope. Ultimately, 60 Hz was chosen in North America, Brazil and Japan and 50 Hz in most other countries. Today, 16 2/3 Hz (in Europe) and 25 Hz in North America are used in railroads, and 400 Hz is a common frequency aboard ships, aircraft and oil rigs.
Too low a frequency, for example, 10 or 20 Hz. is not useful for illumination purposes because the human eye will perceive a flicker. On the other hand, the frequency again cannot be too high because magnetization losses increase proportionally with frequency and eddy current losses even with the square of frequency. Yet there is also an advantage to using a higher mains frequency: motors, generators and transformers can be made smaller while maintaining rated power. For the majority of applications, 50 or 60 Hz as a frequency standard is a nice compromise.
