## 4 Simulation Analysis  
This section is dedicated to simulating the proposed diagnostic method in order to confirm the theoretical assumptions presented in the previous section. The simulation studies and respective results were achieved using the software _Matlab/Simulink_. It was adopted the four-phase 8/6 _SRM_ model that is available at the _Simscape Simulink Library_. The characteristics of the machine are presented in Table 2. The proposed method was tested for different operating conditions of the _SRM_ considering different transistor failure modes and different devices. The first simulation test was made for the proposed detection method considering an open-circuit failure mode under a 600 rpm motor speed. To verify the dynamic behavior of the fault detection method, the motor was operating initially with the drive in normal condition (without failures) and at \(t=1\) s, where \(t\) denotes time, an open-circuit failure in the upper transistor of phase \(A\) (\(S_{1A}\)) was introduced. Figure 6 shows the motor winding currents before and after the failure. The corresponding \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Operation Mode** & \(SI_{A}\) & \(SI_{B}\) & \(SI_{C}\) & \(SI_{D}\) \\ \hline Normal operation & 1 & 1 & 1 & 1 \\ Open-circuit failure & 0 & \(>\)1 & \(>\)1 & \(>\)1 \\ Short-circuit & \(>\)1 & \(<\)1 & \(<\)1 & \(<\)1 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Values of the Diagnostic Variables for the Several Operation Modes Associated with Phase \(A\). \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Value** \\ \hline Number of stator poles & 8 \\ Number of rotor poles & 6 \\ Rated power (\(kW\)) & 1 \\ Peak current (A) & 10 \\ Rated speed (r/min) & 2850 \\ Phase resistor (\(\Omega\)) & 1.3 \\ Inertia (kg.m.m) & 0.01 \\ Friction (N.m.s) & 0.005 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Characteristics of the motor. result of the diagnostic variables generated by the proposed algorithm is presented in Figure 7. As shown in this figure, after the fault the diagnostic variable associated with the motor phase connected to the leg of the open transistor will change immediately their value from one to zero. The other diagnostic variables will also change from one to a higher value (1.3). This confirms what was expected for the diagnostic variable behavior for this failure mode. A test for the same fault but for an increased motor speed (600 rpm) was also realized. In this test, the fault happened in a different power device, more specifically the one associated with phase A (\(S_{1A}\)). The obtained result of the motor winding currents can be seen in Figure 8. As in the previous case, the fault appeared at \(t=1\) s. Analyzing the obtained result it is possible to verify that the result is similar with the previous case, although now the current frequencies are higher and the phase under fault is another one. In Figure 9 is shown the obtained diagnostic variables regarding this specific test. From this result is possible to confirm that only the diagnostic variable associated with the leg under fault will present a higher change after the fault (from 1 to 0). The other diagnostic variables also show a change after the fault, but in an opposite direction and with a lower variation (from 1 to 1.3). Figure 6: Motor winding currents of the switched reluctance motor (\(SRM\)) at 60 rpm in normal condition and open-circuit failure of power device \(S_{1D}\) (simulation result). Figure 7: Diagnostic variables associated with the motor winding currents of the \(SRM\) at 60 rpm in normal condition and open-circuit failure of power device \(S_{1D}\) (simulation result). Another simulation test, considering again an open-circuit failure, was performed but in this case for 1200 rpm. In this case it was considered a failure in a different power device (\(S_{1B}\)).