Frequency converter refers to a class of electrical machinery that was used to convert one frequency (Hertz) of electrical power into another frequency. A typical use is for running non-US machinery which requires 50 Hz power where utility power was supplied as 60 Hz current.
The standard power in the U.S. is usually 60 Hz, but in much of Europe, and other parts of the world, the standard is 50 Hz, thus factories which want to manufacture products in the U.S. for export to a country which has the standard of 50 Hz will need a frequency converter that converts 60 Hz power to 50 Hz power. This is also true for factories in countries which have a standard of 50 Hz manufacturing products which need to be tested for use in the U.S. at 60 Hz.
Another application is in the Aerospace and Airline industries. Often Airplanes use 400 Hz power so 50 Hz or 60 Hz to 400 Hz Frequency converter is needed for use in the ground power unit used to power the airplane while it is on the ground.
The most common use for a frequency converter is to control the speed of three phase induction motors. The speed of an induction motor is given by the formula
Ns = 120F / p
where
Ns = Synchronous speed, in revolutions per minute F = AC power frequency p = Number of poles per phase winding
The frequency of the AC power can be adjusted with a frequency converter and the speed of the induction motor will change accordingly to the formula above.
