PWM frequency

Contrary to the common misunderstanding of many, the mains power line frequency is NOT precisely controlled at any instant in time, or over the course of any given day . When demand is high, generators slow down substantially. The result of this load is that mains power line frequency drops–and often, dramatically.

In large parts of the world this is 50 Hz , although in the Americas and parts of Asia it is typically 60 Hz. Current usage by country or region is given in the list of mains electricity by country.

The voltage quoted is the root mean square, and the peak voltage can be calculated by multiplying the voltage with 2 , or the peak-to-peak voltage is found by multiplying with 2 2 . The frequency used in mains electricity is either 50Hz (20ms period) sinusoidal or 60Hz (16.66ms period) sinusoidal.

50Hz corresponds to 3000 RPM . That range is a convenient, efficient speed for the steam turbine engines which power most generators and thus avoids a lot of extra gearing. 3000 RPM is also a fast, but doesn’t put too much mechanical stress on the rotating turbine nor AC generator.