MODULATION STRATEGIES FOR A NEW SCR-BASED INDUCTION-MOTOR DRIVE SYSTEM WITH A WIDE SPEED RANGE

A new SCR-based naturally commutated induction motor drive that provid es high torque over a wide speed range is presented. Topology is simil ar to that of certain naturally commutated current source inverters, b ut modulation techniques and system performance are very different. Tw o novel switching algorithms are proposed to cover the low-speed and h igh-speed regimes. Torque ripple is negligible in the low-speed region . With these two switching techniques, commutation is reliable and ope ration within peak device voltage stress limits is guaranteed. For ind uction machine loads, this drive has the torque-speed capability typic al of a cycloconverter (but with far fewer devices), plus a field weak ening range that the cycloconverter does not have. Simulation and expe rimental results are presented.