A case study of replacing steam turbines with LCI type variable speed drives

The authors describe the problems and experiences associated with the installation, startup, and operation of 7000 hp, 1800 r/min and 3600 hp, 6000 r/min synchronous motors using LCI (load commutated inverter) variable-speed controllers. Some of the problems and concerns that were encountered on this project were a result of existing equipment worked with, coupled with the dynamics of the electrical, instrumentation, and process systems. It is concluded that, when planning the application of variable-speed drives, factors such as electrical system disturbances, the impact of harmonics on the existing equipment, training, commissioning, operator acceptance, craft training, and spare parts all need to be taken into consideration. If properly designed and installed, these drive systems provide an economical, reliable, variable-speed package for petrochemical installations including large critical applications