## 3 Algorithm and Scheme of Diagnostics of Asymmetric Emergency Modes
### Diagnostic Scheme for Asymmetric Emergency Modes
Due to the above, current values of active resistances \(\mathrm{r_{sa}}\), \(\mathrm{r_{sb}}\), \(\mathrm{r_{sc}}\) of stator phases were added to this block as the input signals, and the amplitudes \(\psi_{\mathrm{sa}}\), \(\psi_{\mathrm{sb}}\), \(\psi_{\mathrm{sc}}\) of phase flux linkages of the stator were added to this block as the output signals. Signals \(\psi_{\mathrm{sa}}\), \(\psi_{\mathrm{sb}}\), \(\psi_{\mathrm{sc}}\) from \"Observer of torque and flux\" and signals \(\mathrm{I_{sa}}\), \(\mathrm{I_{sb}}\), \(\mathrm{I_{sc}}\) from the output of the autonomous voltage inverter are fed to the \"Block for diagnosing emergency asymmetric modes\". The curves of phase currents and flux linkages of the stator are of non-sinusoidal character as the autonomous voltage inverter is used in the DTC traction drive system based on the PWM sampling in its operation algorithm. In view of this factor, the module \"Fast Fourier Transform Block\" was used to determine the components of the amplitude-frequency spectra of phase currents and flux linkages. Besides the implementation of standard algorithm Fast Fourier Transform, the algorithm of identification of the first harmonic component (component on the main feed frequency) was added to the module \"Fast Fourier Transform Block\". The obtained signals are fed into the module \"Calculation of average values of currents and flux links\". The mean values of phase currents and flux linkages of the stator for the time equal to five periods of variation of the feed voltage are calculated in the module \"Calculation of average values of currents and flux links\" of the block. The obtained signals are fed into the module \"Compare block\" for comparison with signals \(\left\lvert\psi_{\mathrm{sset}}\right\rvert\) and \(\left\lvert\mathrm{I_{sset}}\right\rvert\). The signal of the determined value of the stator current \(\left\lvert\mathrm{I_{sset}}\right\rvert\) is calculated in the module \"Block for determining the set value of the stator current\" where expression (19) is implemented. Signals are fed from the output of the model \"Compare block\" to the module \"Decision block\", where the algorithm represented in Equations (3)-(18) is implemented. The results of diagnosis from the model \"Decision block\" are fed to the \"Display block\" that reflects the information on the presence (absence) of the asymmetric emergency modes in the traction drive system elements. In the presence of asymmetric emergency modes, the \"Display block\" reflects the information on the element and the phase of the traction drive element subjected to the damage. Block diagram \"Block for diagnosing emergency asymmetric modes\" is presented in Figure 12.  
The structural block diagram of the DTC system with the block for diagnosis of the asymmetric emergency modes is presented in Figure 13.  
Figure 12: Structural block diagram for diagnosis of the asymmetric emergency modes. Figure 13: Structural block diagram of the DTC system with the block for diagnosing of the asymmetric emergency modes. Hence, the diagram (Figure 13) enables diagnosing the asymmetric emergency modes that occur in the traction drive system and separating them from the asymmetric modes caused by the transient processes.