I am reviewing a motor stator harmonics faults and I am having some difficulties with the identification of stator slot harmonics frequencies or trying to properly identify a stator faults in the analysis!
I have reviewed Ronald L. Eshelman VI book and the equation that he provided has few explanation of its source or the definition of the variables like the "n"!
First stator harmonics =
((2 x n x S)-1)/ P
Second stator harmonics =
((2 x n x S)+1)/ P
S is the number of slots
n suspect the line frequency "but not certain" so 60hz
P Number of poles
Can any one help me find the source or explain the equation for the value of "n" and the reasons for the + or - 1.
Also I am not certain that this could be measured during bearing vibration surveys because of the low amount of energy from a stator slots electric fault or resonance!
Any comments would help!