The optimization of the single/two phase induction motor start-up with electronically switched capacitor

The single/two phase induction motor startup is usually done by connecting the auxiliary winding of the motor to the mains; to provide the phase-shift of the auxiliary supply voltage with respect to the mains voltage, a series capacitor, also called the split capacitor is connected with the named winding. In steady state operation the auxiliary winding is switched-off or a run-capacitor is connected to reduce currents through the auxiliary winding. To optimize the efficiency of the drive both at startup and in steady-state operation various structures have been proposed and presented in literature. A simple structure is the use of an electronically switched capacitance instead the fixed split capacitance. The command strategy of the electronically switched capacitance pursues to achieve a maximum of the electromagnetic torque during the process. Within the paper the transient response analysis is used to deduce the estimated transfer function of the switched capacitance-induction motor-load system. Based on these determinations the controllerpsilas transfer function may be deduced to optimize the dynamics of the drive.