# Mechanical Faults Analysis in Switched Reluctance Motor
## 4 Discussion  
This work presents the results of two diagnostic experiments on a reluctance motor: dynamic eccentricity damage and imbalance. The test results were presented as the current signal and acceleration (vibration) spectra. The load torque and motor speed values were changed during each experiment.  
The first test was the diagnosis of the dynamic eccentricity of the SRM for a displacement value of 0.25 mm. The most precise and interesting results could be observed in the current spectrum at the lowest SRM rotational speed of 400 rpm. For both motor operating states, the sixth and, to a lesser extent, eighteenth and thirtieth peaks (third and fifth multiplications of the sixth peak) are visible on the graph (since the SRM has six poles on the rotor); another interesting phenomenon appears in the state with a given fault. Namely, in the vicinity of the principal sixth harmonic, two high peaks (the fifth and seventh peaks, respectively) appear on both sides of it and, to a lesser extent, between the sixth and first harmonics, the value of which also increases noticeably. This phenomenon is an effect of amplitude modulation.  
It is worth noting that this phenomenon decreases slightly at higher rotational speeds, but when there is no load, it disappears altogether.  
The eccentricity experiment consisted of setting the length of the air gap varying in time, and the magnetic field also varied in time. This was the original physical reason for  
Figure 19: Acceleration spectra for three torque load values with imbalance “B” and at 1000 rpm rotational speed.  
Figure 18: Current spectra for three torque load values with imbalance “B” and at 1000 rpm rotational speed.  
this fault, which also caused the remaining operating quantities, such as the current and electromagnetic torques, to be sinusoidally variable in time.  
The phenomena of nonlinearity occurring in the motor was justified by amplitude modulation in the signal.  
The vibration signal from the accelerometer confirmed these results. The exact correlation of the amplitude of the tested signal can be seen depending on the value of the load torque and the rotational speed, as in the case of the current signal. Indeed, the information from the acceleration sensor was more distorted, probably due to the test station's impact and the motor's inherent features. Nevertheless, because the current spectrum was incomparably more evident, the analysis was focused on it. However, there are some methods still to be used to study the spectrum of accelerations and their filtration; further research may be carried out.  
Two types of damage were introduced for the imbalance experiment: A and B. The graphs show almost no differences between the motor operating states. The spectra are precise, with the sixth harmonic clearly visible (and its third and fifth multiples are slightly duplicated).  
While studying dynamic eccentricity presents interesting nonlinear phenomena, the imbalance study does not illustrate any particular differences between the correct operation and the one with a given fault.  
The design based on the disc did not allow the imbalance phenomenon to be shown reliably, or it did not show specific properties in the signal. To obtain more convincing results, it would be necessary to use larger screws to be screwed into the disc or to reconstruct the disc itself and the stand.