A frequency converter is an electronic device that converts alternating current of one frequency to alternating current of another frequency. The device may also change the voltage, but if it does, that is incidental to its principal purpose.

Frequency converters vary in power-handling capability from a few watts to megawatts. Frequency converter are built out of electromechanical components as motor-generator sets or rotary converters.

Frequency Converter Motor Generator Sets are used for converting power frequency, voltage and phase. With frequency this is most often 50Hz or 60Hz utility line frequency power over to 50Hz, 60Hz, or 400Hz power to run equipment. In addition to this, frequency converter motor generator sets also offer line isolation, harmonic cancellation, power factor correction, phase conversion, voltage conversion with balanced, smooth, controlled power output. Typical applications include AC variable speed drives, inverters, computers and computer controlled equipment, deep well pumps, industrial machinery and many more. 400Hz Frequency Converters are most often used for Aerospace or Aircraft to keep planes powered up when on the ground in ground power units.

Frequency changers are typically used to control the speed of pumps and fans. In many applications significant energy savings are achieved. The most demanding application areas are found on the industrial processing lines, where the control accuracy requirements can be very high.

Voltage-to-frequency converters can receive AC or DC voltage inputs and output frequencies or pulse signals by using techniques such as amplitude modulation (AM), frequency modulation (FM), and pulse width modulation. Some voltage-to-frequency converters send outputs to timers, counters, relays, switches, and potentiometers. Others can output voltage ranges such as 0 – 10 V or current loops such as 4 – 20 mA. Integral filters allow some frequencies to pass while attenuating others. Programmable filters allow users to set and change parameters such as the low pass frequency, the nominal frequency below which input signals are passed and above which input signals are blocked.