Soft Start/Adjustable Speed Systems for Multiple MW Rated Motors

Conventional starting and adjustable speed drive technologies for MW-size applications are overviewed. The latest medium voltage static frequency converter technologies are summarized and it is shown that some topologies can eliminate most disadvantages associated with conventional technologies. Application examples including reactor, motor generator, and load commutated inverter starting are described. Technology now exists with MW power ratings producing a near sinusoidal high output voltage that is suitable for both synchronous and induction motors. An application concept is described that utilizes these advantages where a static frequency converter is used to start several motors and to drive one motor at adjustable speed. Additional benefits are described in terms of hazardous areas, system fault level, lifetime and capital cost of equipment, switching surge overvoltages and conditioning monitoring. A case study is presented that includes integration possibilities with existing and future systems. Conclusions and recommendations for future work and development are provided