## 5 Results
### Motor Working under Low-Load (Low-Saturation) Conditions  
The second study focuses on the detection of eccentricity faults when the analyzed fPMa-SynRM works under low-load conditions, and thus, less saturation. This study assumes that the operating conditions are 0.7 A\({}_{\text{RMS}}\), 130 V\({}_{\text{RMS}}\), 5000 rev/min, and 40\({}^{\circ}\) current angle (between _d_-0\({}^{\circ}\) and _q_-90\({}^{\circ}\)). It is noted that a low current means a low magnetic saturation of the rotor segments.  
Figure 7 shows the spectral content of the line currents of the analyzed fPMa-SynRM working under low-current and low-saturation conditions, for both healthy and 40% static eccentricity conditions.  
Figure 8 shows the spectral content of the ZSVC of the analyzed fPMa-SynRM working under low-current and low-saturation conditions, for both healthy and 40% static eccentricity conditions.  
As proved in Figures 7 and 8, the discrimination power decreases (both healthy and faulty spectra are almost superimposed) with respect to the operating point corresponding to the nominal conditions, since almost all of the magnetic flux flowing through the stator windings is due to the permanent  
Figure 8: Low-current low-saturation operating conditions. Spectral content of the ZSVC. Healthy machine and faulty machine with 40% eccentricity.  
Figure 7: Low-current low-saturation operating conditions. Spectral content of the line currents. Healthy machine and faulty machine with 40% eccentricity.  
magnets in the rotor, and thus, the reluctance of the path followed by the magnetic flux in the rotor is high compared to the reluctance of the air gap, thus hindering the detection of such faults.  
Motor Working under Low-Load (Low-Saturation) and near d-Position (Current Angle 30\({}^{\circ}\))  
In order to improve the sensitivity of the methods based on the line currents and ZSVC, the motor is analyzed when positioned close to the \(d\) axis. In this position, the influence of the permanent magnets can be almost neglected, and the reluctance of the rotor path is still lower than the reluctance of the air gap, thus facilitating the detection of the analyzed faults. In addition, the low current level produces a low magnetic saturation of the rotor segments. This study assumes that the operating conditions are 0.7 A\({}_{\text{RMS}}\), 150 V\({}_{\text{RMS}}\), 5000 rev/min, and 30\({}^{\circ}\) current angle.  
Figure 9 shows the spectral content of the line currents of the analyzed fPMa-SynRM working under low-current low-saturation conditions with a current angle of 30\({}^{\circ}\), for both healthy and 40% static eccentricity conditions.  
In this operating point, there are significant differences in the third, ninth, seventeenth, and nineteenth harmonics of the line currents, thus enabling the detection of eccentricity faults.  
Figure 10 shows the spectral content of the ZSVC when the motor operates under low-current conditions with a current angle of 30\({}^{\circ}\). It shows substantial differences in the third, fifth, and fifteenth harmonics of the ZSVC.  
Figure 10: Low-current low-saturation operating conditions with a current angle of 30\({}^{\circ}\). Spectral content of the ZSVC. Healthy machine and faulty machine with 40% eccentricity.  
Figure 9: Low-current low-saturation operating conditions with a current angle of 30\({}^{\circ}\). Spectral content of the line currents. Healthy machine and faulty machine with 40% eccentricity.