Sensorless operation of a thyristorized commutatorless series motor drive

This paper presents a new strategy of implementing a sensorless, load-commutated, thyristorized inverter-driven commutatorless series motor (CLSM) drive. The drive is started with the help of a position encoder, but, after four-five cycles, the operation is changed over to the "sensorless running" mode at about 10% of rated speed. The strategy, description and illustrative waveforms of the sensorless implementation are presented, followed by the description of the scheme of changeover from the "start" to the "sensorless running" mode. Results of the experimental studies of the sensorless drive are presented. Finally, important features of this sensorless implementation are mentioned.