Concept, design and testing of a 12MW 9500 RPM induction motor with oil film bearings for pipeline applications in North America

Abstract

Directly coupled converter-fed electric motors for oil & gas applications, especially for pipeline and process compressors, have become more common in recent years due to increased efficiency and precise process control. The pipeline industry is demanding more Megawatts at higher speeds, which means large high-speed electric motors are used in applications directly coupled to high-speed centrifugal compressors, which in the past have been traditionally driven by large gas turbines. Motor manufacturers developed specifically designed motors for applications such as these instead of using higher-speed standard motors. These efforts in recent years resulted in a reliable and optimized motor design, especially the rotor-bearing design, enclosure, bearing shields and cooling to meet stringent vibration and noise requirements, which are defined in specifications such as API, IEC and ISO. Depending on the end user and application, the bearings of motors such as these still represent a challenge. Either active magnetic bearings (AMB) or oil film bearings can be used and the motor needs to provide the interface for both. Design philosophy and technology are applied to design and test 12 MW induction motors running in oil film bearings with a speed range of 4500-9500 rpm for a specific power, torque and speed to replace obsolete and underperforming motors at a natural gas interstate pipeline compressor station in the USA.