Considerations in the Design of VFD Motor-Driven Compressors

Abstract

Tutorial 17: The various drivers for process compressor trains are designed in accordance with the pertinent process requirements. In the case of variable speed applications for process compressors, Steam turbines or Gas turbines are typically applied as a standard practice. However, improvements in inverter technology have made Variable Frequency Drive (VFD) motors a viable solution for variable speed applications. Motor drivers are well suited for constant speed applications, but VFD motor drive systems represent a relatively new technology for process compressor applications, so the technical differences and associated risks need to be well understood by Users, EPC contractors and Turbomachinery OEM’s. Any misunderstanding or miscommunication among any of these parties could lead to a worst case scenario of machine damage and unexpected plant shutdowns. This paper addresses the basics of VFD technology from a practical as well as technical point of view with the overall aim of helping to pre-empt worst case scenarios.