Performance analysis of AC chopper fed AC series motor using microcontroller

AC series motors are extensively employed in many industrial applications such as portable drills, sewing machines, food mixers and hand tools requiring high starting torque. Armature voltage control is an effective and simple method of speed control in most of these applications. Solid state AC voltage controllers can be used to control the voltage applied to the motor. AC voltage controllers with back to back connected SCRs or TRIACs employing phase control strategy are commercially available for this purpose. However the controllers are found to create problems like introduction of harmonics in the input supply, poor supply power factor and inference to communication equipments. These problems are severe at large firing angles of the controller. The problems introduced by phase control method can be overcome if pulse width modulation technique is employed for the speed control of AC series motor. With pulse width modulation (PWM) chopper control, the harmonic distortion can be reduced and the power factor can be improved. Multiple pulse width chopper employing selective harmonic elimination strategy is employed can further reduce the harmonics.