An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 1) SPECTRUM ANALYSIS <s> Theaimofthis paper istopresent theresults ofsimulation Abstract --Diagnostic methodofelectrical faults inswitched andlaboratory condition research inthescope oftheanalysis reluctance motors (SRM)based oncurrent harmonics analysis is ofhigher harmonics content, foundinthecurrent andtorque presented inthispaper. Theclassification ofelectrical faults in waveforms oftheswitched reluctance motorsoperating at SRM'shasbeendiscussed, simulation modelandlaboratory selected electrical failure modes. setup presented. FortheSRM motorof6/4design theconclusions drawnfromthetestsconducted bothinthesimulated and P Sioppiy hwetr motor laboratory conditions forregular operation and selected electrical faults. Theelectrical fault typefoundinthemachine plil- wasdetermined onthecontent ofharmonics ofhigher orderin thesourcecurrent. Theconclusions arcincluded. IndexTerms-- Switched Reluctance Motor, SRM,electrical2 faults, harmonic analysis, diagnostics. <s> BIB001 </s> An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 1) SPECTRUM ANALYSIS <s> The concept of fault tolerance device and implementation of the automated algorithm based fault detection plays an important role in the reliable operation of rotating machinery. This paper looks at fault tolerant power converter failure detection in three-phase 6/4 switched reluctance machine (SRM) through the use of time-frequency technique for the detection of power switch open-circuit failure. A fault tolerant power converter with redundancy and specific winding connections has been proposed for a three-phase 6/4 switched reluctance machine in order to add fault tolerant capacity to a standard three-phase SRM converter and also for improving the reliability of motor. This is achieved by using a dual converter on a common power supply with six isolated phases. The power converter model is built up in CIRFLU using Flux 2D's electrical circuit and linked to the finite elements method (FEM) model of the SR machine. Power switch open-faults occurrences in a fault tolerant power converter are considered and the effect on the electromagnetic torque signal is analyzed using various time-frequency representations (TFR). The results prove the efficiency of the proposed approach in automatic detection and localization fault in power converter phase. Simulation results are presented and well discussed. <s> BIB002 </s> An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 1) SPECTRUM ANALYSIS <s> Linear induction motors (LIMs) are being gradually applied in the urban rail transit due to their simplified mechanical structure and feasibility for both low-speed and high-speed operations. Direct-torque control (DTC) is a classical control scheme that can be readily extended to LIMs. However, due to the high thrust ripple and poor dynamic performance for the low-speed operation, control performance of DTC is not satisfactory. This paper is to propose an explicit model predictive control to be combined with the DTC scheme. First, the LIM model is presented and discretized. Then, the LIM drive and its operating principle are discussed. Thirdly, the controller design, including control variables, and the objective function are depicted. Finally, both the simulation and the experiment are engaged for verifying the proposed control algorithm. <s> BIB003 </s> An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 1) SPECTRUM ANALYSIS <s> Reliability of power converters is of crucial importance in switched reluctance motor drives used for safety-critical applications. Open-circuit faults in power converters will cause the motor to run in unbalanced states, and if left untreated, they will lead to damage to the motor and power modules, and even cause a catastrophic failure of the whole drive system. This study is focused on using a single current sensor to detect open-circuit faults accurately. An asymmetrical half-bridge converter is considered in this study and the faults of single-phase open and two-phase open are analysed. Three different bus positions are defined. On the basis of a fast Fourier transform algorithm with Blackman window interpolation, the bus current spectrums before and after open-circuit faults are analysed in details. Their fault characteristics are extracted accurately by the normalisations of the phase fundamental frequency component and double phase fundamental frequency component, and the fault characteristics of the three bus detection schemes are also compared. The open-circuit faults can be located by finding the relationship between the bus current and rotor position. The effectiveness of the proposed diagnosis method is validated by the simulation results and experimental tests. <s> BIB004 </s> An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 1) SPECTRUM ANALYSIS <s> Winding short-circuit is one of the more common faults in switched reluctance motors (SRM). This paper takes an in-depth look at winding short-circuit. The characteristic of non-sinusoidal intermittent single phase current, fundamental components are extracted to reconstruct four phase symmetrical currents based on spectrum analysis of phase currents. The method of symmetrical component is used to calculate positive and negative sequence components of reconstructed currents, where then the ratio between positive and negative sequence component is seen as a fault feature and the diagnostic criterion is proposed. The simulation and experimental results are presented to confirm the implementation of the proposed method. <s> BIB005 </s> An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 1) SPECTRUM ANALYSIS <s> Thermal analysis is an important issue in machine design which allows to have a knowledge of the machine temperature rise. This paper presents the thermal analysis, modeling, and experiments of a linear-switched reluctance machine (LSRM) with toroidally wound mover and segmental structure. First, a 3-D heat flow model with the homogenized region for the presented LSRM is established using the thermal equivalent circuit. The equivalent thermal resistance of the model is developed together with the nodes forming of the thermal resistance network. The thermal identification to each component such as windings and core steel is performed. Then both the numerical 2-D and 3-D heat flow model for the presented LSRM are established by finite-element analysis which can give the detailed temperature distribution of the entire machine. At last, the actual experiment on a prototype is carried out, validating the accuracy, and feasibility of the thermal equivalent model above. <s> BIB006 </s> An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 1) SPECTRUM ANALYSIS <s> With the increasing proliferation of variable speed drive, the demand for the more reliable drive is also on the rise. Despite the growing interest on more advanced motors like permanent magnet and flux switching motors, three-phase induction motors (3ph-IMs) are still the main workhorse in the industry and hence the fault-tolerant control of these motor drives remains an interesting and important topic. In this paper, a simple fault-tolerant field-oriented control technique for 3ph-IMs is presented. It is shown that by injecting zero-sequence compensation voltage in a feedforward manner, open-circuit faults can be effectively tolerated. Compared to the previous feedforward fault-tolerant control methods, the proposed approach does not require the knowledge of the magnetizing inductance, which is tricky to be obtained in induction motors. Furthermore, the unified feedforward approach allows the same control structure to be used for different fault-tolerant 3ph-IMs drive topologies, with minor modifications to the feedforward terms. In addition, the effect of inverter non-idealities on the performance of the proposed control method is also highlighted and addressed. The effectiveness of the proposed controller is verified using MATLAB simulation and further validated using experimental tests. This paper is accompanied by a video demonstrating the experimental results. <s> BIB007
In SRM drive systems, phase currents are discontinuous and unidirectional, and their fundamental frequency is related to the rotating speed of the motor, given by. where f is the fundamental frequency of the phase current, n is the motor speed, and N r is the number of the rotor pole. To extract the amplitude of the fundamental signal, fast Fourier transformation (FFT) is used to the measured signal. The Fourier transformation can be expressed as (5) Short-circuit fault can be diagnosed through the FFT method  . The simulation waveforms of phase currents in normal and short-circuit condition are given in Fig. 4 . The peak current value after fault becomes much larger than the normal peak current, resulting in heat dissipation problems and device damage issues. The post-fault torque ripple increases dramatically compared to pre-fault situation and the negative torque is generated in the inductance decreasing region, which seriously deteriorates the output torque of the SRM. In BIB005 , four kinds of symmetrical components are deduced, including the zero sequence I A(0) , positive sequence I A BIB003 , negative sequence I A BIB007 , and half-zero-sequence I A(3)  where I A , I B , I C , and I D are reconstructed four-phase current vectors expressed by fundamental component amplitude in a trigonometric function form. Then, a fault index defined as the ratio of positive and negative-sequence components of the reconstructed current. The ratio equals to 0.5 in normal condition and will decrease with the number of shorted turns. Finally, the short-circuit fault can be detected by judging whether the fault index equals to 0.5. Open-circuit faults can also be diagnosed by the FFT approach with a single current sensor BIB004 , where the Blackman window function is employed for FFT due to lower errors caused by spectrum energy leakage and picket fence effect. For open-circuit faults, the faulty phase is uncontrollable and the current inevitably decreases to zero, losing the ability to generate the phase torque. Hence, the average torque becomes lower with larger torque ripple as presented in Fig. 5 . In BIB004 , the open-circuit fault can be easily diagnosed and located by monitoring the dc, fundamental, and second harmonic components of the current spectrum with the bus current sensor. Six kinds of open-and short-circuit fault occurring in different power devices are analyzed by FFT in BIB001 . By performing the FFT analysis on the bus current and comparing amplitudes of several specific harmonics, fault conditions can be accurately recognized from normal condition. However, some kinds of opening faults cannot be distinguished from each other. Another spectrum analysis method for fault diagnosis is time-frequency representation (TFR), which is proposed in BIB002 . The main idea of this technique is to execute two kinds of TFR strategies, as illustrated in Fig. 6 . The smoothed Wigner-Ville distribution (SPWVD) is represented by W P (t,f) in BIB006 and the Cohen's class distribution (CCD) is denoted by (8) These two formulas aim at extracting fault signatures from the torque, because the frequency response of the torque changes in pre-and post-fault situation. The SPWVD is used to accomplish the mission of the open-circuit fault detection, and the CCD is combined with Fisher's discriminant to distinguish different open-circuit faults. Through the procedure exhibited in Fig. 6 , open-circuit faults detection and identification can be effectively achieved.