Single phase AC-AC converter with improved power factor for efficient control of fan motors

Conventional single phase AC voltage controllers using TRIAC are used for the speed control of single phase induction motor for fan applications. Such drive suffers from disadvantages such as higher torque oscillations, low input power factor and higher dv/dt across motor at low speed. These disadvantages are more prominent in low motor speed. This paper deals with the direct ac to ac variable voltage control drive with only two power semiconductor switches associated with Diode Bridge to overcome above drawbacks. The most prominent feature of presented drive is leading and high input power factor besides smooth speed control. This is achieved by using the extinction-angle control (EAC) control technique. In this paper, the modes of operation of presented drive along with the performance evaluation of the EAC technique and conventional phase angle control (PAC) technique has been illustrated.