Apparatus and method for diagnosing rotor shaft

A method of diagnosing a rotor shaft, installed in a bearing so that the rotor shaft is rotated around an axis of rotation, using an apparatus for diagnosing a rotor shaft, the method comprising:

• measuring first vibration signals at two points of the rotor shaft located on a surface perpendicular to the axis of rotation;
• calculating second vibration signals, which are vibration signals at points located in a plane including the two points of the rotor shaft at which the first vibration signals are measured, based on the first vibration signals;
• generating an image based on the second vibration signals;
• and
• diagnosing the rotor shaft based on the generated image,
• wherein calculating the second vibration signals comprises
• calculating vibration signals at points that have been rotated from any one point, at which a corresponding one of the first vibration signals is measured, around the axis of rotation by a predetermined angle of rotation one or more times, as the second vibration signals,
• generating the second vibration signals only at points within a range corresponding to a semicircle of a surface perpendicular to the axis of rotational, and
• inferring such that the second vibration signals within the range corresponding to the remaining semicircle, except for the semicircle, have opposite phases of the same size compared to signals at symmetrical points with respect to the center of an axis.