Electronic Frequency Converter

An electromechanical frequency converter are used within motor generator sets or rotary converters. Frequency converter may also be solid state electronics. Solid state electronics devices normally employ a rectifier (producing direct current) which is inverted to produce AC of the desired frequency. The inverter may use thyristors or IGBTs. A battery may also be incorporated within the DC circuit to improve the converter's demand performance during short input power outages. Frequency converters are available in many power handling capacity from a few watts to megawatts, as well as, different frequency ranges.

Frequency converters are used to convert power from one distribution standard to another, frequency converters are also used to control the speed and the torque of AC motors. In this application, the typical frequency converter is a three-phase two-level voltage source inverter. The phase voltages are controlled by using power semiconductor switches and a Pulse Width Modulation (PWM). Semiconductor switching devices and anti-parallel connected freewheeling diodes are combined to form a bridge, which is used to connect all motor phases to the positive or negative dc-link voltage. The PWM changes the connections of the phases between the positive and the negative DC-link valtage so that the wave voltage has the desired frequency. Frequency converters are commonly used to control the speed of pumps and fans. Significant energy and power savings are achieved in many applications.

Standard industrial, aviation, and European frequency converters operate at 50 Hz, 60 Hz, and 400 Hz (Aircraft and Shipboard).