Slip-power recovery scheme employing a fully controlled convertor with half-controlled characteristics

The major disadvantage of the slip-power recovery scheme using the static Scherbius scheme is its poor power factor at low speeds. In the investigation presented in the paper, a fully controlled inverter with half-controlled characteristics has been employed for improving the power factor instead of the conventional fully controlled inverter. Considerable improvement in the power factor of the motor and drive was obtained. There was an increase in efficiency of the drive and a reduction in the ripple current in the DC link current. The paper also presents a new method for starting the motor and a criterion for selection of filter inductance. Equations have been derived for calculating machine performance and drive power factor. The various theoretical deductions have been verified experimentally.