Diagnostic apparatus, diagnostic method, recording medium having recorded thereon diagnostic program, and power conversion apparatus including diagnostic apparatus

A non-transient recording medium having recorded thereon a diagnostic program that is executed by a computer and causes the computer to:

• control a motor to rotate;
• acquire target data relating to a current value between a power conversion apparatus and the motor;
• detect at least three latest peak values in a time series waveform of the target data;
• use a frequency counting method to calculate an amplitude of each of the at least three latest peak values and a frequency of occurrence of the amplitude of the at least three latest peak values;
• diagnose an abnormality of the motor based on the calculated amplitude of the at least three latest peak values and the frequency of occurrence of the amplitude of the at least three latest peak values;
• and
• stop the rotation of the motor based on the diagnosed abnormality, wherein
• the amplitude of each of the at least three latest peak values is an absolute value of a difference in amplitude between two adjacent ones of the at least three latest peak values, and
• a weight of either 0.5 cycle or 1.0 cycle is assigned to each of the at least three latest peak values.