AC to AC Conversion

A cycloconverter or a cycloinverter converts an AC voltage such as the mains supply to another AC voltage. The amplitude and the frequency of input voltage to a cycloconverter tend to be fixed values, whereas both the amplitude and the frequency of output voltage of a cycloconverter tend to be variable. On the other hand, the circuit that converts an AC voltage to another AC voltage at the same frequency is known as an AC chopper.
 
A typical application of a cycloconverter is to use it for controlling the speed of an AC traction motor and most of these cycloconverters have a high power output, of the order a few megawatts and SCR's are used in these circuits. In contrast, low cost, low power cycloconverters for low power AC motors are also in use and many of these circuits tend to use triods for alternating current (TRIAC) in place of SCR's. Unlike an SCR which conducts in only one direction, a TRIAC is capable of conducting in either direction and like an SCR, it is also a three terminal device. It may be noted that the use of a cycloconverter is not as common as that of an inverter and a cycloinverter is rarely used.