Mechanical and Electrical Considerations of Electric Motor/Drivers for Large Centrifugal Compressors in Ethylene Cracker Applications.

Traditionally, large centrifugal compressor drivers used in Ethylene cracker applications are steam turbine drives. This has been a natural choice due to the availability of steam generated as part of the cracking process. For very large capacity plants, these steam turbine drivers are required to produce powers in excess of 100 MW. Recently, due to the clean energy initiatives, there seems to be a trend in the industry to apply electric motors for these ethylene cracking applications in lieu of steam turbine drivers. Large electric motors with VFD drivers brings its own challenges, limitations etc. In this paper, the authors will take a detail look at the mechanical challenges including but not limited to start-up demands and their impact on compressor selections, transient torsional requirements and also a detail review of electric motor/drive requirements, suitability of drive technology (LCI vs. VSI), experience trends, reliability and availability considerations. The paper also briefly outline the optional testing requirements including complete unit test and what extent of electrical and mechanical scope to be included.