Load Commutated Inverter (LCI) fed synchronous motor drives are popular in high power, Medium Voltage (MV) industrial applications. However, in spite of the lower cost and greater ruggedness of induction motors, LCI fed induction motor drives are not generally used. The main reason behind this is the lagging power factor characteristic of the induction motor which makes load commutation difficult in these drives. The dual-stator Active-Reactive Induction Motor (ARIM) introduced in literature provides an induction motor drive using LCI converter topology. Here the stator is built with an additional low voltage winding which supplies reactive power to the machine using a connected IGBT-VSI. This topology is an attractive solution for MV drives as it combines the advantages of thyristors and induction motors. But the ARIM has some disadvantages in terms of size, efficiency and torque ripple when compared to conventional induction motors.



In this work, two new configurations of ARIM based topologies namely Tapped Stator ARIM (TS-ARIM) and Split Phase ARIM (SP-ARIM) are proposed to overcome the disadvantages of the conventional ARIM drive. In the TS-ARIM configuration, a low voltage tap on the main stator winding is used to connect the VSI. There is no separate low voltage winding as in the ARIM. This results in better material utilization and lower losses compared to the ARIM. The SP-ARIM configuration uses a split-phase winding configuration on the stator connected to a 12-pulse LCI. The 12-pulse operation combined with harmonic cancellation from the VSI results in a drive with a very smooth torque ripple, especially in the low-speed ranges.



A new technique for reliable thyristor commutation in LCI fed ARIM based drives, is also proposed in this work. The proposed technique enables full torque operation of the drive at extremely low speeds. A novel thyristor-based CSI fed drive topology is also developed based on the proposed commutation technique.



All the proposed topologies and control techniques have been verified using a 75 kW, 3.3 kV rated ARIM drive, with a low voltage winding of 400 V. The critical design aspects of the machine are also discussed, and the results obtained from hardware implementation of the proposed methods are presented.