The Application of Laser Tracker Measurements and Induction Heating for Re-shrinking a Rotor Rim

摘要

The process of re-shrinking a rotor rim requires a minimum of the following steps: (1) heating the rim to remove the shrinkage keys, (2) measuring the gap between the rim and head beam, and (3) heating the rim to place in new shrinkage keys. Laser measurements and induction heating are presented as means for accomplishing the aforementioned steps. A distinct advantage of laser measurement is it allows the rim and head beam keyway positions to be determined relative to the rotor centerline (common reference) in a straightforward manner. Thus, the shrinkage keys thickness can be adjusted to compensate for differences due to keyway machining and rim lamination position. A disadvantage of the laser is the environment must be constant throughout the measurements. Induction heating has an advantage over resistance heating as is it produces almost no stress gradients. Because induction utilizes the losses inherent in the rim material to generate heat, the temperatures externally and internally are nearly uniform. This minimizes the chances to distort the rim. A disadvantage of induction is the B-H curve for rim steel is not always known. The following paper presents this alternate method. Further, it presents how the disadvantages were overcome along with field data of a rim shrink.