Lateral rotor vibration (LRV) is radial-plane orbital motion of the rotor spin axis. Transverse rotor vibration is used synonymously with LRV. Figure 2.1 shows the sketch of a complete steam turbine generator rotor (minus turbine blades) and a sample of its computed LRV vibration orbits, shown grossly enlarged. Actual LRV orbits are typically only a few thousandths of an inch (a few hundredths of a millimeter) across. LRV is an important design consideration in many types of rotating machinery, particularly turbo-electrical machines such as steam and combustion gas turbine generators sets, compressors, pumps, gas turbine jet engines, turbochargers, and electric motors. Thus, LRV impacts several major industries.