SE-14-016 -- Installation and Results of Variable-Frequency Drives at a Mid-Sized Power Generation Facility

Originally a mid-sized Midwestern U.S. power plant controlled airflow rate used for combustion by dampers. This airflow rate that travels through the boiler and scrubber pollution control device is provided by centrifugal blowers powered by two 4000 hp (3.0 MW) and two 3000 hp (2.2 MW) motors. Variable-frequency drives (VFDs) were installed to power these motors and analysis was made by examining the electrical current of the motors approximately one year before and after VFD installation. After installation, the VFD was operated manually and airflow was still partially controlled by the dampers, hence not saving the maximum amount of electricity. Even operating this way, however, the analysis showed that the VFDs saved 22.76 GWh annually. This power plant assumes a cost of $0.04/kWh for electricity produced, therefore, the project saves $910,440 annually and the total project cost was $2.9 million. In addition, grants providing $2 million of these funds greatly improving the profitability. The project was a success, providingVFDs with a long life expectancy that saves a significant amount of electricity for an appropriate initial cost.