Significance level:
A significance level (α) of 0.05 is established.
Calculation of p value:
Since this is a right-sided test, the p-value is calculated using Student's t-table with 12 degrees of freedom
and finding the area in the tail of the test statistic t = 2.49. In this case, the p value is 1.782 in table.
The null hypothesis is rejected and the alternative hypothesis is accepted. This means that there is sufficient
evidence to conclude that the Daubechies wavelet diagnostic method does have a significant effect on the
identification of low insulation faults in low voltage electric motors.
CONCLUSIONS
Daubechies Level 8 Wavelet analysis is presented as a novel and effective tool for diagnosing low insulation
faults in the stator coils of squirrel cage rotor induction motors, both at low and medium voltage. This
technique, based on the analysis of the stator current signal during the start-up transient, allows low
insulation faults to be accurately identified through characteristic changes in the wave spectrum and energy
distribution of the current signals. Levels of detail 8, 7, 6 and 5 are particularly relevant for the detection of
these faults. The detail curve patterns vary significantly in the failed engine with respect to the healthy
engine. The wavelet histograms show a difference in the distribution of energy levels between the healthy
and the failed motor, indicating a greater tendency towards higher wavelet coefficient values in the failed
motor. The student’s t test for a single sample demonstrates that wavelet transform diagnosis does have a
significant effect on the identification of faults due to low insulation in low voltage electric motors. Unlike
traditional static-state insulation testing, Daubechies Level 8 Wavelet Analysis offers early and accurate fault
detection, even in the presence of low insulation values. This capability opens a promising path for the
implementation of the method in condition monitoring systems, improving predictive maintenance
practices and reducing the incidence of catastrophic failures in electric motors. This study provides strong
evidence supporting Daubechies Level 8 wavelet analysis as a valuable tool for the diagnosis and prevention
of low insulation faults in induction motors.
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