An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 1) CURRENT PROFILING <s> The switched reluctance drive is known to be fault tolerant, but it is not fault free. The goals of this study are the systematic classification of all electrical faults, short-and open-circuits, in the switched reluctance drive (excluding the controller itself), and the investigation of fault patterns and possible remediation. Each situation is analyzed via finite element analysis, and/or experiments. The transient effects during the faults are described. Possible remediation schemes other than disabling the faulted phase are explored. There is a particular focus on switch short-circuit for which new results are presented. <s> BIB001 </s> An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 1) CURRENT PROFILING <s> A concept of an integrated and distributed inverter for switched reluctance machines is introduced. The application at hand is an outer-rotor direct drive designed for railway traction applications. A five-phase switched reluctance machine (SRM) was developed and is used to demonstrate the function of the integrated and distributed inverter. The distribution is achieved by supplying each phase coil with its own modular inverter. Each inverter module is placed evenly around the end of the stator stack next to its dedicated coil. This increases the redundancy of the drive significantly. The likelihood of phase-to-phase faults is reduced, because no overlapping end-turns are necessary. Also, the integration of machine and inverter is simplified, because the semiconductors can be evenly distributed around the machine. The concept reduces the amount of terminals between drive and vehicle to communication, power supply and cooling, independent of the number of machine phases. With the integrated and distributed inverter new control strategies can be developed to influence machine vibration and radiated noise. In this paper the design of the prototype, the direct torque control of the five-phase machine and the behavior in case of a fault inside a module is analyzed. <s> BIB002 </s> An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 1) CURRENT PROFILING <s> This paper presents a new fault diagnostic technique applied to switched reluctance motor drives, based on the analysis of the power converter supply current. A fault is detected when the measured amplitude of the dc bus current differs from its expected amplitude, assuming normal operating conditions. The information about phase currents amplitudes and the control commands of all power switches permit to easily estimate the amplitude of the power converter supply current, since an asymmetric bridge converter is used. Simulation and experimental results are presented. Open- and short-circuit fault occurrences in the converter power switches are considered and analyzed. The proposed technique can early detect these fault occurrences and can also identify the affected motor phase. In almost all situations, the faulty element is also identified. An early fault diagnosis, with an accurate fault identification, is of a paramount importance since it permits the early adoption of fault-tolerant procedures that minimize the fault impact on the machine operation. <s> BIB003 </s> An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 1) CURRENT PROFILING <s> This paper presents a new method for noninvasive diagnosis of static, dynamic, and mixed eccentricity faults in switched reluctance motors (SRMs). This method makes it possible to precisely determine the eccentricity fault features. The proposed signature in this algorithm is based on the analysis of produced current with a particular variation pattern. It is theoretically shown that the occurrence and growth of the fault level cause an increase in amplitude of the produced current signature (PCS), which can be employed to diagnose the fault and extract its details. In this method, first, occurrence of the fault and its location are detected by utilizing eccentricity level detection pattern. Afterward, a new index to precisely determine the fault level is introduced. Then, a novel strategy based on the proposed pattern and index is offered to detect the type of eccentricity as well as the exact location of the faulty phase. For this purpose, an SRM under eccentricity fault is modeled using three dimensional transient finite element method (TFEM). This precise model considers all complex motor geometry, nonlinear characteristics of the motor, end effects and axial fringing effects. A test bed in the laboratory is established to perform various measurements on the eccentric motor with different fault levels. The experimental results validate the numerical analysis outcomes. Fault detection and analysis in SRM demonstrate that the algorithm presented can assure the reliability of detection as well as the sensitivity of eccentricity fault in a SRM. <s> BIB004 </s> An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 1) CURRENT PROFILING <s> In safety-critical systems, faults can cause life losses, environmental degradation, or significant financial losses. In this paper, a segmental stator switched reluctance machine is proposed for such applications. A short overview of its design is given. Its fault tolerance is investigated by dynamic simulations and laboratory tests. It is demonstrated via both methods that the proposed machine is able to have a continuous operation despite five severe winding fault conditions. <s> BIB005 </s> An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 1) CURRENT PROFILING <s> This paper describes four main fault types of the asymmetric bridge power converter in switched reluctance motor drive on power transistors. Two on-line fault diagnosis methods for power transistors in the power converter are proposed. The principle of the proposed diagnosis methods is to detect the real-time current state from some particular positions, and then obtain the diagnosis result and the fault location by logical judgment. One fault diagnosis method is proposed using single current sensor monitoring the chopped bus current; the other method is using dual current sensors scheme monitoring the upper freewheeling bus current and excitation bus current. The simulation results of current states from certain positions of a three-phase 12/8 motor and its power converter are analyzed. Experiments have verified the effectiveness of the proposed fault diagnosis methods. It is shown that the dual current sensors scheme monitoring the upper freewheeling bus current and excitation bus current has the fastest fault response. <s> BIB006 </s> An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 1) CURRENT PROFILING <s> Brushless dc (BLDC) motors are commonly used in space application for its simplicity and high reliability. The fault-tolerant control (FTC) of the motor is important for its continuous operating capacity even under the faulty situation. The fault diagnosis should be achieved in advance in order to implement the FTC strategy. This paper proposes an online model-based inverter fault diagnosis method for three-phase full bridge inverter with buck dc-dc converter based on the high-speed BLDC motor with low inductance and nonideal back electromotive force in a magnetically suspended control moment gyro. The method can detect and identify both open-circuit and short-circuit damages of single switch in buck converter or three-phase full bridge. Also, protective measures are proposed to isolate the fault and avoid the secondary fault. Both simulation and experimental results are taken out to prove the validity and effectiveness of the proposed fault diagnosis method. <s> BIB007 </s> An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 1) CURRENT PROFILING <s> Electrical failure of power converter will greatly affect switched reluctance motor (SRM) systems. Based on four typical faults, the fault procedure and consequence of power converter are analyzed in detail. Due to obvious fault characteristics of the freewheeling current, this paper proposes a fault diagnosis scheme based on the freewheeling current. Power converter operates in excitation phase and freewheeling phase and faults happening during different phases will result in change in freewheeling current. Fault characteristics are obtained on the basis of changes of the freewheeling current and transformed to electrical lever jumping based on digital thought to obtain a effective fault diagnosis scheme will. Finally, the scheme will be verified through simulation experiments. The results show that this scheme utilizes more fault characteristics and diagnoses faults more accurately compared with the fault diagnosis scheme based on only phase current. <s> BIB008 </s> An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 1) CURRENT PROFILING <s> Nowadays is necessary to increase reliability and fault-tolerance of technical equipment that integrated in dangerous facilities such as both nuclear, military, chemical, petroleum etc. It is most pressing to electric drive mechanisms with full or partial functional recovery. In article shown fault-tolerant control algorithms of switched-reluctance motor drive in emergency modes. These algorithms based on activation of functional backup by either increasing phase currents amplitudes or increasing phases overlap angles or both of them. Under review the comparative analysis of these algorithms based on simulation in MatLab Simulink are shown. Full or partial functional recovery of switched-reluctance motor drive under single or multiple failures such as losing phase or converter switches failures are described. <s> BIB009 </s> An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 1) CURRENT PROFILING <s> In order to take advantage of conventional switched reluctance motors (SRMs), the SRM is integrated with the bearingless motor technology and then a reluctance type of bearingless motor is created, named as bearingless SRM (BSRMs). Not only electromagnetic torque but also the levitation forces should be controlled in BSRMs, which is different from SRMs. The levitation forces should always exist even when winding fault occurs. Therefore, the absent levitation forces that ought to be produced by the fault winding should then be compensated by other winding. This paper proposes the compensation strategy of levitation forces for BSRMs when one stator winding is short circuited. The short-circuit fault is investigated and the short-circuit current is expressed for the derivation of radial forces. Then, the winding compensation rule and the mathematical model of levitation forces are developed to facilitate the compensation control for the motor levitation. After that, the proposed compensation strategy is verified by simulation results in MATLAB/Simulink. Experimental results are also presented to demonstrate the performance. <s> BIB010 </s> An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 1) CURRENT PROFILING <s> This study presents a novel phase current reconstruction strategy for switched reluctance machines (SRMs) using two cross-winding current sensors. The phase currents are reconstructed by solving the linear equations associated with two adjacent phase currents in the different turn-on regions. The effect of current sensor offset and power transistor fault on the proposed reconstruction method is analysed. On the basis of the current difference at the rising edge of each drive signal, an offset sensor identification method is presented and two online compensation schemes are adopted. For power transistor short-circuit fault, the logic-judgment-based and freewheeling-time-based diagnostic methods are investigated and a virtual current sensor is introduced to ensure the effectiveness of the reconstruction process. The proposed phase current reconstruction strategy is free from power transistor open-circuit fault. In addition, the current reconstruction method is easily extended to SRMs with higher number of phases without additional current sensors. Simulations and experiments validate the effectiveness and flexibility of the proposed reconstruction strategy. <s> BIB011 </s> An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 1) CURRENT PROFILING <s> This paper focuses on a minimal current sensing strategy and fault detection of switched reluctance machines (SRMs). In order to reduce the number of required current sensors in multiphase motor drives, the optimal selection and location of current sensors is presented in consideration of the precise actual phase current measurement, open- and short-circuit fault detection. The proposed scheme requires two current sensors to replace the phase current sensors placed in each phase without any additional devices for multiphase SRMs to achieve a more compact and low-cost drive. Different current regulation methods are employed for single phase conducting region and commutation region. To obtain the phase currents from the proposed approach, different settings of the pulsewidth modulation signals for adjacent phases during the commutation region are implemented. The simulation and experiments on a four-phase 8/6 pole SRM are carried out to verify the effectiveness of this approach in the healthy and faulty cases. <s> BIB012 </s> An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 1) CURRENT PROFILING <s> Detection of winding faults in permanent magnet synchronous machines (PMSMs) with stranded winding designs remains a challenging task for conventional diagnostic techniques. This paper proposes a new sensing approach to this problem by investigating the application of dedicated electrically non-conductive and electromagnetic interference immune fiber Bragg grating (FBG) temperature sensors embedded in PMSM windings to enable winding open-circuit fault diagnosis based on observing the fault thermal signature. The final element analysis thermal and electromagnetic models of the examined practical PMSM design are first developed and used to enable the understanding of open-circuit winding fault-induced signature that can be used for effective diagnostic purposes, indicating in situ thermal excitation as an optimal diagnostic measurand. A purpose build test rig with an inverter-driven commercial PMSM instrumented with in situ FBG sensors monitoring phase winding hot spots is then used to evaluate the efficacy of the proposed diagnostic scheme. It is shown that unambiguous diagnosis and severity trending of winding open-circuit faults is enabled by the use of in situ FBG sensors. A comparison with conventional fault diagnostic technique utilizing current signal sensing and analysis is also reported, indicating the considerable advantages of the proposed monitoring scheme employing FBG sensors. <s> BIB013
In BIB006 , four types of power transistor faults in AHB converter, including the upper switch open-circuit fault, upper switch short-circuit fault, lower switch open-circuit fault, and lower switch short-circuit fault, are diagnosed with one current sensor. The differential value of lower freewheeling bus current I fdn and upper freewheeling bus current I fup , i.e., chopped bus current, is represented as The chopped bus current is a sequence of jumping signal. Through monitoring and detecting abnormal value of the chopped bus current, the above four types of power transistor faults can be accurately diagnosed. By detecting the freewheeling current on the basis of digital method, five states including normal state and four typical fault states are recognized according to the digital number, which is acquired by comparing the freewheeling current with the threshold BIB008 . An enhanced fault diagnosis method with minimal current sensing strategy is reported in BIB012 . A low-cost current sensor placement is employed for the phase current measurement exhibited in Fig. 8 . The reconstructed phase currents are compared with the thresholds to obtain the setting fault flag to indicate the open-and short-circuit faults. The slope of phase currents in excitation, freewheeling, and demagnetization states are quite different. Based on the voltage equation, the gradient of phase currents can be calculated. In BIB011 , the fault signal µ combining the gradient of the phase currents λ and chopping signals P is described in BIB013 to diagnose the upper-switch short-circuit fault. And the lower-switch short-circuit fault is detected by comparing the freewheeling time of different phase currents. Another remarkable fault diagnosis scheme is based on estimated and measured dc bus currents BIB003 . The diagram of the fault diagnosis scheme is illustrated in Fig. 9 , where the parameter k is selected by empirical formula BIB007 . This scheme is proved to be robust and accurate experimentally. Numerical computation under various degree of the eccentricity fault is researched in BIB004 . When phase A is aligned, the sinusoidal test signal is injected into phase B. Then numerical analysis towards induced currents in phase A and phase C are employed. Then, the same procedures are employed when phase B or phase C is at the aligned position. In BIB005 , the torque ripple under normal condition and opencircuit fault situation is decreased by tracking the command current obtained from the current table I = f (T , θ). Two current tables are pre-acquired for normal and open-circuit fault operation to minimize the torque ripple, which is derived from finite element modeling analysis. In BIB002 , an integrated inverter with pole distributed configuration is invented for switched reluctance traction drive with fault-tolerant ability. When one pole module is broken-down, the unbalanced magnetic force and vibration can be mitigated by blocking the opposite module to restore the symmetric excitation. A current profiling fault-tolerant strategy is investigated in BIB009 by enlarging the command value of phase currents and expanding the conduction period. The current profiling strategy can also be applied to compensate the levitation forces when winding short-circuit fault happens BIB010 . When one stator winding is fully shorted, the levitation force will be synthesized by short-circuit current in faulty winding and compensation current in adjacent phase winding. The currents in short-circuit winding and compensation winding are analyzed by mathematical model and accurately injected into the corresponding phase windings. The control diagram of this current profiling strategy is presented in Fig. 21 . Owning to the inherent fault-tolerant feature of the SRM, the open-circuit fault can be viewed as an automatic loss of the faulty phase. The short-circuit fault tolerance control is achieved in BIB001 based on turning off the faulty switches in advance to eliminate the peak current. However, disabling faulty phase switches for short-circuit fault-tolerance control is more advantageous than turning off switches in advance because of its high efficiency in the same operating point.