Design and Shop Testing of a 165kW Cryogenic Expander/Generator on Magnetic Bearings

A low cost cryogenic expander system that incorporates a high performance, high-speed permanent magnet generator and low loss magnetic bearings is described. The expander system will be used in industrial air separation plants that produce gases such as nitrogen, oxygen, and argon using a cryogenic distillation process. Magnetic bearings enable the key advantage of a completely oil-free system that reduces the risk of accidental contamination of the process. A single generator/bearing module was designed to accommodate a wide range of expander aerodynamic stages that operate at different speeds and power levels ranging from 9,000 RPM to 30,000 RPM and 10 kW to 165 kW. Shop testing of the unit to 30,000 rpm was completed in December 2003. The prototype unit will undergo additional loop testing at the system manufacturer’s facility and is scheduled for field installation in mid 2004. System design and test results are presented.