In this topic, you study AC to AC converter – Definition & Theory.
An AC to AC converter can be cycloconverter or AC voltage controller.
Cycloconverter
A cycloconverter is an electrical circuit, converts a fixed voltage and fixed frequency AC to a variable voltage and variable (lower) frequency AC. The output voltage is controlled by varying the firing delay angle. It can be used to generate a constant frequency, constant voltage from a variable frequency AC source. The cycloconverter principle is widely used in the following applications:
(a) Speed control of large AC drives like rotary kilns, etc.
(b) Static variable speed constant frequency (VSCF) generators for aircraft as shown in the block diagram of Fig. 1.7.
Fig. 1.7 AC to AC frequency changer system
AC voltage controllers
An AC voltage controller is an electrical circuit, converts a fixed voltage AC to a variable voltage AC. Variable voltage AC output is used for lighting control, speed control of fans, fractional horse power AC motors, three-phase induction motors, and for smooth induction motor starting. Three-phase AC voltage controller with Y-connected load is shown in Fig. 1.3.