# Seven-Phase PMSM Drives Operation Post Two Types of Faults
## 5 Simulation Results of the Seven-Phase Drive after Losing Phase 'A' and the Speed Sensor  
The closed-loop speed control of the seven-phase drive post the failures in phase 'A' and the speed sensor has been simulated using SABER simulator based on the control structure shown in Figure 18. The NSV-SVPWM in addition to the saliency tracking algorithm proposed in [38] will be used if the motor is operated without faults. When the failure in phase 'A' is introduced, then the new SVPWM technique proposed in Section 3 and the new algorithm to track the saliency proposed in Section 4 will be used. The figures below demonstrate the performance of the seven-phase drive after losing phase 'A' and losing the speed sensor due to the faults at different load and speed conditions. Figure 19 shows the response of the seven-phase drive post the faults at low speeds. From the beginning until \(t=3\) s, the motor was operating at speed \(=-30\) rpm without faults. At \(t=3\) s, the speed of the drive was reversed while the motor still running without faults. Then at \(t=4.5\) s, phase 'A' was lost due to the fault while the new SVPWM was used to assure the minimum inverter current optimization. After that, at \(t=6\) s and while phase 'A' was still lost, the speed of the drive was reversed again. At \(t=7\) s, an additional fault was introduced to the operation of the motor drive which is the failure in the speed sensor (i.e., the motor became running under the failures in phase 'A' and the speed sensor). Finally, at \(t=9\) s, and while the motor was running post the two failures, the speed of the motor drive was reversed for the third time. The results show the dynamic response in addition to the steady-state response of the whole drive post the two failures were as good as that obtained without failures. Moreover, the result proves the significant increase in the robustness of the drive by using the new SVPWM and the new technique to track the saliency. Figure 18: Speed control structure of the seven-phase drive after the faults. Figure 20 shows a similar result to those obtained in Figure 19 but at higher speed steps. The drive was operating without faults at zero speed. At \(t=2\) s, the speed of the motor drive was changed to 240 rpm. Then, at \(t=3\) s, a fault in the speed sensor was introduced to the drive. Hence, the motor speed and position were obtained using the algorithm proposed in [36]. After that, two-speed steps from 240 rpm to 0 and from 0 to \(-240\) rpm were applied to the motor drive while the speed sensor is still a failure. At \(t=7\) s, an additional failure in phase 'A' was introduced to the motor and the motor became running under the failures in the speed sensor in phase 'A'. It should be mentioned here that after phase 'A' was disconnected, the new SVPWM proposed in this paper was used to assure the minimum inverter current optimization and at the same time, the algorithm proposed in this paper was used to obtain the rotor position and rotor speed. Finally, at \(t=8\) s, the reference speed of the motor drive was changed to 0. The dynamic and the steady-state responses of the whole drive system illustrated in Figure 20 post the failures were at the same quality of the response of the drive system when running without faults. Figure 21 illustrates the robustness of the seven-phase drive when a load disturbance is applied post the failures. The motor was running at \(-90\) rpm without faults. At \(t=2\) s, phase 'A' was disconnected due to an open-circuit fault. After that and while the phase 'a' was disconnected, a load disturbance was applied to the seven-phase drive and then removed between \(t=3\) s and \(t=4.5\) s. Then the motor speed was controlled to 0 rpm at \(t=6.5\) s. While the motor was running at zero speed and phase 'A' was disconnected, an additional fault was introduced to the seven-phase drive at \(t=7\) s which was the fault in the speed sensor. At \(t=7.5\) s the speed of the motor was controlled to 90 rpm.