**3.5. Experimental verification**

To verify the effectiveness of the proposed scheme experimentally, a test rig for testing a 750- W SRM prototype is set up, as shown in Figure 21(a). Two air switches are adopted to emulate open-circuit and short-circuit faults, as shown in Figure 21(b), where *J*<sup>1</sup> is used to achieve an open circuit fault and *J*2, a short circuit fault. Figure 21(c) shows the fault tolerance control system diagram with the closed-loop speed regulation capability. As illustrated in the figure, a PI controller is used to regulate the motor speed, and the proportional gain and integral gain are 0.05 and 0.5, respectively. The current controller and voltage controller are utilized to generate the drive signals to control the motor drive in different operation modes. The position detector and speed calculator are used to give the instantaneous speed for feedback control. The current sampling and fault diagnosis schemes are employed to control the gate signals for the fault tolerant topology to operate under faulted conditions.

The type of the MOFESTs used is FDA59N30 from Fairchild Inc; and diodes are IDW75E60 from Infineon Technologies. Three current sensors (LA55Ps) are used to measure the phase currents. An incremental encoder with 1000 lines is used to measure the rotor position. A dSPACE 1006 control board is employed to implement the control scheme. A magnetic brake acts as the load with a torque of 1 N·m. The dc-link voltage is fixed to 48V. Two air switches are adopted to generate open-circuit and short-circuit faults. The torque observed in the oscilloscope is obtained online by using the real-time phase currents and rotor position to look up for the torque value in a 3D torque table that includes the *T*-*i*-*θ* characteristics [18, 19]. The torque data in the lookup table are measured by using a rotor-clamping device when supplying different steady currents to the motor windings in a rotor position that changes step-by-step. The output torque in the experimental waveforms is observed through a D/A converter.

The turn-on and turn-off angles are set to 0° and 20°, respectively. In voltage-PWM control system with fault tolerant topology, the turn-on angle is set to 5° to improve the phase current balance for the fault tolerance performance when the short-fault occurs. Figures 22 through 25 present the experimental results at 500 r/min, where *ia*, *ib*, and *ic* are the phase currents for phase A, B, and C, respectively; *T*\* and *T* are the given load torque and instantaneous torque, which show a good agreement with the simulation results. Figure 22 presents the typical voltage-PWM control model waveforms of the SRM under normal, open-circuit fault, and short-circuit fault conditions. In a normal condition, three phases have the same current amplitude and shape. In an open-circuit faulty condition, there is no current in the faulty phase. In a shortcircuit faulty condition, the faulty phase current cannot decrease to zero. The experiment results have agreed well with the analytical study in Section 3.3. Figure 23 verifies the control strategy under fault condition. By controlling the turn-on angle of phase A, the output torque ripple can be decreased. Figure 24 shows the typical waveforms for the current regulation control model under normal, open fault, and short fault conditions. In an open-circuit faulty condition, there is no current in the faulty phase, while in a short-circuit faulty condition, as theory analysis, the fault phase current cannot decrease to zero. The experiment results also verify the theory analysis in Section 3.2. Under these fault tolerance operation conditions, the faulty phase current and output torque with the proposed method can follow the reference values faithfully, as shown in Figure 25. This is also the case in reducing the torque ripple and the imbalance between phase currents for conventional converters with either open-circuit or short-circuit faults. experiment results have agreed well with the analytical study in Section 3.3. Figure 23 verifies the control strategy under fault condition. By controlling the turn-on angle of phase A, the output torque ripple can be decreased. Figure 24 shows the typical waveforms for the current regulation control model under normal, open fault, and short fault conditions. In an open-circuit faulty condition, there is no current in the faulty phase, while in a short-circuit faulty condition, as theory analysis, the fault phase current cannot decrease to zero. The experiment results also verify the theory analysis in Section 3.2. Under these fault tolerance operation conditions, the faulty phase current and output torque with the proposed method can follow the reference values faithfully, as shown in Figure 25. This is also the case in reducing the torque ripple and the imbalance between phase currents for conventional converters with

(c) Diagram of the fault tolerance control system Figure 21. Experimental setup and the control system.

15

either open-circuit or short-circuit faults.

the short-circuit fault of the drive happens, the demagnetization current cannot decrease to zero due to a zero-voltage loop, which causes phase current to become more unbalanced and

Considering the proposed fault tolerance scheme in the CCC system, a half of the failure phase still can be put into use to ensure the torque output. Since the phase current is the control target, it will be regulated to the same reference compared to the normal one, even though a half of the failure phase is removed. In voltage-PWM control strategy, the phase voltage is the control target. The imposed voltage on each phase is the same, regardless of the whole or half of the phase winding works. In order to reduce the unbalanced phase current further in voltage-PWM system, the turn-on angle of the failure phase can be adjusted lagging behind to reduce the increased phase current in the failure winding, as illustrated in Figure 20(b). Hence, the proposed drive topology can be used to compensate the current and torque, and reduce the

To verify the effectiveness of the proposed scheme experimentally, a test rig for testing a 750- W SRM prototype is set up, as shown in Figure 21(a). Two air switches are adopted to emulate open-circuit and short-circuit faults, as shown in Figure 21(b), where *J*<sup>1</sup> is used to achieve an open circuit fault and *J*2, a short circuit fault. Figure 21(c) shows the fault tolerance control system diagram with the closed-loop speed regulation capability. As illustrated in the figure, a PI controller is used to regulate the motor speed, and the proportional gain and integral gain are 0.05 and 0.5, respectively. The current controller and voltage controller are utilized to generate the drive signals to control the motor drive in different operation modes. The position detector and speed calculator are used to give the instantaneous speed for feedback control. The current sampling and fault diagnosis schemes are employed to control the gate signals for

The type of the MOFESTs used is FDA59N30 from Fairchild Inc; and diodes are IDW75E60 from Infineon Technologies. Three current sensors (LA55Ps) are used to measure the phase currents. An incremental encoder with 1000 lines is used to measure the rotor position. A dSPACE 1006 control board is employed to implement the control scheme. A magnetic brake acts as the load with a torque of 1 N·m. The dc-link voltage is fixed to 48V. Two air switches are adopted to generate open-circuit and short-circuit faults. The torque observed in the oscilloscope is obtained online by using the real-time phase currents and rotor position to look up for the torque value in a 3D torque table that includes the *T*-*i*-*θ* characteristics [18, 19]. The torque data in the lookup table are measured by using a rotor-clamping device when supplying different steady currents to the motor windings in a rotor position that changes step-by-step. The output torque in the experimental waveforms is observed through a D/A converter.

The turn-on and turn-off angles are set to 0° and 20°, respectively. In voltage-PWM control system with fault tolerant topology, the turn-on angle is set to 5° to improve the phase current balance for the fault tolerance performance when the short-fault occurs. Figures 22 through 25 present the experimental results at 500 r/min, where *ia*, *ib*, and *ic* are the phase currents for phase

and *T* are the given load torque and instantaneous torque, which

torque ripple to improve the drive performance in fault conditions.

the fault tolerant topology to operate under faulted conditions.

obviously increases the torque ripple.

78 New Applications of Electric Drives

**3.5. Experimental verification**

A, B, and C, respectively; *T*\*

either open-circuit or short-circuit faults.

Figure 21. Experimental setup and the control system.

experiment results have agreed well with the analytical study in Section 3.3. Figure 23 verifies the control strategy under fault condition. By controlling the turn-on angle of phase A, the output torque ripple can be decreased. Figure 24 shows the typical waveforms for the current regulation control model under normal, open fault, and short fault conditions. In an open-circuit faulty condition, there is no current in the faulty phase, while in a short-circuit faulty condition, as theory analysis, the fault phase current cannot decrease to zero. The experiment results also verify the theory analysis in Section 3.2. Under these fault tolerance operation conditions, the faulty phase current and output torque with the proposed method can follow the reference values faithfully, as shown in Figure 25. This is also the case in reducing the torque ripple and the imbalance between phase currents for conventional converters with

Figure 22. Experimental results of voltage-PWM control mode under normal and fault conditions. **Figure 22.** Experimental results of voltage-PWM control mode under normal and fault conditions. Figure 22. Experimental results of voltage-PWM control mode under normal and fault

conditions.

(a) Normal (b) Open fault

15

Fault Diagnosis of Switched Reluctance Motors in Electrified Vehicle Applications http://dx.doi.org/10.5772/61659 81

Figure 24. Experimental results of current regulation control mode without fault tolerance topology under fault conditions. **Figure 24.** Experimental results of current regulation control mode without fault tolerant topology under fault condi‐ tions.

Figure 26 shows the fault tolerance operation at 500 r/min and 5 N·m load in CCC **Figure 25.** Experimental results of current regulation control mode with fault tolerant topology under fault conditions.

and PWM systems, respectively. The system can still be stable when operating at large load and make up for the missing output torque of the fault phase. Figure 27 shows the operation of the developed system during acceleration and at high speeds with a 1 N·m load. As illustrated in Figure 27(a), the speed follows the given value well during the continuous acceleration progress. In Figure 27(b), the system is still stable when it is operated at 1500 r/min, which shows a good stability at high speeds.

16

15

15

experiment results have agreed well with the analytical study in Section 3.3. Figure 23 verifies the control strategy under fault condition. By controlling the turn-on angle of phase A, the output torque ripple can be decreased. Figure 24 shows the typical waveforms for the current regulation control model under normal, open fault, and short fault conditions. In an open-circuit faulty condition, there is no current in the faulty phase, while in a short-circuit faulty condition, as theory analysis, the fault phase current cannot decrease to zero. The experiment results also verify the theory analysis in Section 3.2. Under these fault tolerance operation conditions, the faulty phase current and output torque with the proposed method can follow the reference values faithfully, as shown in Figure 25. This is also the case in reducing the torque ripple and the imbalance between phase currents for conventional converters with

Figure 21. Experimental setup and the control system.

experiment results have agreed well with the analytical study in Section 3.3. Figure 23 verifies the control strategy under fault condition. By controlling the turn-on angle of phase A, the output torque ripple can be decreased. Figure 24 shows the typical waveforms for the current regulation control model under normal, open fault, and short fault conditions. In an open-circuit faulty condition, there is no current in the faulty phase, while in a short-circuit faulty condition, as theory analysis, the fault phase current cannot decrease to zero. The experiment results also verify the theory analysis in Section 3.2. Under these fault tolerance operation conditions, the faulty phase current and output torque with the proposed method can follow the reference values faithfully, as shown in Figure 25. This is also the case in reducing the torque ripple and the imbalance between phase currents for conventional converters with

(a) Normal (b) Open fault

(c) Short fault Figure 22. Experimental results of voltage-PWM control mode under normal and fault conditions.

Figure 21. Experimental setup and the control system.

Figure 22. Experimental results of voltage-PWM control mode under normal and fault conditions.

(a) Turn‐on angle is 0° for phase A (b) Turn‐on angle is 5° for phase A Figure 23. Experimental results of voltage-PWM control mode with fault tolerance topology under fault conditions.

**Figure 23.** Experimental results of voltage-PWM control mode with fault tolerant topology under fault conditions.

(a) Normal (b) Open fault

**Figure 22.** Experimental results of voltage-PWM control mode under normal and fault conditions.

either open-circuit or short-circuit faults.

80 New Applications of Electric Drives

either open-circuit or short-circuit faults.

Figure 26 shows the fault tolerance operation at 500 r/min and 5 N·m load in CCC and PWM systems, respectively. The system can still be stable when operating at large load and make up for the missing output torque of the fault phase. Figure 27 shows the operation of the developed system during acceleration and at high speeds with a 1 N·m load. As illustrated in Figure 27(a) , the speed follows the given value well during the continuous acceleration progress. In Figure 27(b) , the system is still stable when it is operated at 1500 r/min, which shows a good stability at high speeds. and PWM systems, respectively. The system can still be stable when operating at large load and make up for the missing output torque of the fault phase. Figure 27 shows the operation of the developed system during acceleration and at high speeds with a 1 N·m load. As illustrated in Figure 27(a), the speed follows the given value well during the continuous acceleration progress. In Figure 27(b), the system is still

stable when it is operated at 1500 r/min, which shows a good stability at high speeds.

Figure 26. Experimental results of fault tolerance operation under the high load. **Figure 26.** Experimental results of fault tolerance operation under the high load. Figure 26. Experimental results of fault tolerance operation under the high load.

Figure 28 shows the fault tolerance operation with only a half phase winding at 500 Figure 27. Experimental results of fault tolerance operation during acceleration and at high-speed operation. **Figure 27.** Experimental results of fault tolerance operation during acceleration and at high-speed operation.

r/min and 1 N·m load in CCC and PWM systems, respectively. The system can still operate with only a half phase winding at light load. Figure 29 shows the fault tolerance operation with only a half phase winding during acceleration and load increasing. The speed still follows the given speed well both during acceleration and in steady state. However, in Figure 29(b), when the load increases from 1 to 3 N·m, Figure 28 shows the fault tolerance operation with only a half phase winding at 500 r/min and 1 N·m load in CCC and PWM systems, respectively. The system can still operate with only a half phase winding at light load. Figure 29 shows the fault tolerance operation with only a half phase winding during acceleration and load increasing. The speed still follows the given speed well both during acceleration and Figure 28 shows the fault tolerance operation with only a half phase winding at 500 r/min and 1 N·m load in CCC and PWM systems, respectively. The system can still operate with only a half phase winding at light load. Figure 29 shows the fault tolerance operation with only a half phase winding during acceleration and load increasing. The speed still follows the given speed well both during acceleration and in steady state. However, in Figure 29(b) , when the load

the speed is reduced due to the insufficient load ability. Hence, in the extreme faulty

in steady state. However, in Figure 29(b), when the load increases from 1 to 3 N·m, the speed is reduced due to the insufficient load ability. Hence, in the extreme faulty

 (a) CCC system (b) PWM system Figure 28. Experimental results of fault tolerance operation with only a half phase winding in the extreme faulty condition at steady-state operation.

conditions, the proposed fault tolerance scheme can still operate at light loads.

conditions, the proposed fault tolerance scheme can still operate at light loads.

16

increases from 1 to 3 N·m, the speed is reduced due to the insufficient load ability. Hence, in the extreme faulty conditions, the proposed fault tolerance scheme can still operate at light loads. increasing. The speed still follows the given speed well both during acceleration and in steady state. However, in Figure 29(b), when the load increases from 1 to 3 N·m, the speed is reduced due to the insufficient load ability. Hence, in the extreme faulty Figure 27. Experimental results of fault tolerance operation during acceleration and at

conditions, the proposed fault tolerance scheme can still operate at light loads.

and PWM systems, respectively. The system can still be stable when operating at large load and make up for the missing output torque of the fault phase. Figure 27 shows the operation of the developed system during acceleration and at high speeds with a 1 N·m load. As illustrated in Figure 27(a), the speed follows the given value well during the continuous acceleration progress. In Figure 27(b), the system is still stable when it is operated at 1500 r/min, which shows a good stability at high speeds.

Figure 26. Experimental results of fault tolerance operation under the high load.

and PWM systems, respectively. The system can still be stable when operating at large load and make up for the missing output torque of the fault phase. Figure 27 shows the operation of the developed system during acceleration and at high speeds with a 1 N·m load. As illustrated in Figure 27(a), the speed follows the given value well during the continuous acceleration progress. In Figure 27(b), the system is still stable when it is operated at 1500 r/min, which shows a good stability at high speeds.

Figure 27. Experimental results of fault tolerance operation during acceleration and at high-speed operation. Figure 28 shows the fault tolerance operation with only a half phase winding at 500 r/min and 1 N·m load in CCC and PWM systems, respectively. The system can still

Figure 28. Experimental results of fault tolerance operation with only a half phase winding in the extreme faulty condition at steady-state operation. **Figure 28.** Experimental results of fault tolerance operation with only a half phase winding in the extreme faulty condi‐ tion at steady-state operation. Figure 28. Experimental results of fault tolerance operation with only a half phase

winding in the extreme faulty condition at steady-state operation.

Figure 29. Experimental results of fault tolerance operation with only a half phase winding during acceleration and load increasing. **Figure 29.** Experimental results of fault tolerance operation with only a half phase winding during acceleration and load increasing.

16

16

#### In this chapter, a novel SRM fault diagnosis and fault tolerance strategy have **4. Conclusion**

**4. Conclusion** 

16

16

Figure 26 shows the fault tolerance operation at 500 r/min and 5 N·m load in CCC and PWM systems, respectively. The system can still be stable when operating at large load and make up for the missing output torque of the fault phase. Figure 27 shows the operation of the developed system during acceleration and at high speeds with a 1 N·m load. As illustrated in Figure 27(a) , the speed follows the given value well during the continuous acceleration progress. In Figure 27(b) , the system is still stable when it is operated at 1500 r/min, which

 (a) PWM system (b) CCC system Figure 26. Experimental results of fault tolerance operation under the high load.

Figure 26. Experimental results of fault tolerance operation under the high load.

**Figure 26.** Experimental results of fault tolerance operation under the high load.

 (a) Acceleration (b) High speed operation Figure 27. Experimental results of fault tolerance operation during acceleration and at high-speed operation. Figure 28 shows the fault tolerance operation with only a half phase winding at 500 r/min and 1 N·m load in CCC and PWM systems, respectively. The system can still operate with only a half phase winding at light load. Figure 29 shows the fault tolerance operation with only a half phase winding during acceleration and load increasing. The speed still follows the given speed well both during acceleration and in steady state. However, in Figure 29(b), when the load increases from 1 to 3 N·m, the speed is reduced due to the insufficient load ability. Hence, in the extreme faulty

 (a) Acceleration (b) High speed operation Figure 27. Experimental results of fault tolerance operation during acceleration and at high-speed operation. Figure 28 shows the fault tolerance operation with only a half phase winding at 500 r/min and 1 N·m load in CCC and PWM systems, respectively. The system can still operate with only a half phase winding at light load. Figure 29 shows the fault tolerance operation with only a half phase winding during acceleration and load increasing. The speed still follows the given speed well both during acceleration and in steady state. However, in Figure 29(b), when the load increases from 1 to 3 N·m, the speed is reduced due to the insufficient load ability. Hence, in the extreme faulty

**Figure 27.** Experimental results of fault tolerance operation during acceleration and at high-speed operation.

Figure 28 shows the fault tolerance operation with only a half phase winding at 500 r/min and 1 N·m load in CCC and PWM systems, respectively. The system can still operate with only a half phase winding at light load. Figure 29 shows the fault tolerance operation with only a half phase winding during acceleration and load increasing. The speed still follows the given speed well both during acceleration and in steady state. However, in Figure 29(b) , when the load

conditions, the proposed fault tolerance scheme can still operate at light loads.

conditions, the proposed fault tolerance scheme can still operate at light loads.

 (a) CCC system (b) PWM system Figure 28. Experimental results of fault tolerance operation with only a half phase winding in the extreme faulty condition at steady-state operation.

and PWM systems, respectively. The system can still be stable when operating at large load and make up for the missing output torque of the fault phase. Figure 27 shows the operation of the developed system during acceleration and at high speeds with a 1 N·m load. As illustrated in Figure 27(a), the speed follows the given value well during the continuous acceleration progress. In Figure 27(b), the system is still stable when it is operated at 1500 r/min, which shows a good stability at high speeds.

and PWM systems, respectively. The system can still be stable when operating at large load and make up for the missing output torque of the fault phase. Figure 27 shows the operation of the developed system during acceleration and at high speeds with a 1 N·m load. As illustrated in Figure 27(a), the speed follows the given value well during the continuous acceleration progress. In Figure 27(b), the system is still stable when it is operated at 1500 r/min, which shows a good stability at high speeds.

shows a good stability at high speeds.

82 New Applications of Electric Drives

In this chapter, a novel SRM fault diagnosis and fault tolerance strategy have been studied. The main contributions of this work are as follows: (i) The fault characteristics under opencircuit, short-circuit faults are researched on the basis of traditional asymmetrical half-bridge

been studied. The main contributions of this work are as follows: (i) The fault

driving topology. (ii) An FFT algorithm with Blackman window interpolation is proposed for SRM fault diagnosis; the method uses the normalized harmonic component of the bus current as the open-circuit fault signature, which can detect the open-circuit faults accurately even in fast transients; the diagnosis time is within one current period, achieving a fast fault detection. (iii) A novel fault tolerance SRM topology is developed with a modular structure. (iv) The developed fault diagnosis technology can achieve convenient fault diagnosis and improve fault tolerance performance of the SRM. Overall, this work will help improve the market acceptance of SRM drives, especially for high-temperature, high-speed, and safety-critical applications.
