Stator Turn Research Articles

Stator Turn Fault Detection by Relative Voltage Residual Slopes With High-Frequency Injection

Stator Turn Fault Detection by Relative Voltage Residual Slopes With High-Frequency Injection

Handling Stray Flux Signals for Stator Turn Insulation Degradation Monitoring

Handling Stray Flux Signals for Stator Turn Insulation Degradation Monitoring

Stator Turn Fault Diagnosis and Severity Assessment in Converter-Fed Induction Motor Using Flat Diagnosis Structure Based on Deep Learning Approach

This work aims to explore the hybrid deep learning techniques for early interturn fault diagnosis and fault severity assessment in variable frequency induction motor drive. However, the existing literature mostly focuses on identifying the fault patterns, whereas the assessment of fault deterioration before it reaches the extreme degradation state has been less investigated. In this paper, a hybrid structure combining two-dimensional convolution neural network (2DCNN) and long-short term memory/gated recurrent unit (LSTM/GRU) has been modelled as a relatively lightweight flat diagnosis structure (FDS) for early fault identification and its severity assessment simultaneously in converter-fed induction motor. Initially, the hierarchical layers of 2DCNN extract the effective features automatically for fault detection and its severity identification simultaneously. Then, these features are presented as suitable inputs to LSTM/GRU for classification. A comparative evaluation of the proposed hybrid method with the standalone structure, namely 2DCNN, LSTM and SVM proves the advantages of the proposed scheme, and its applicability for both fault diagnosis and fault severity assessment in industrial drive systems, under variable frequencies and load variations.

Negative Sequence Current Compensation for Induction Motor Stator Inter-Turn Short Circuit and Off-Diagonal Term in Sequence Impedance Matrix as Fault Indicator

This work proposes an artificial neural network supported method to establish an automatic detection of stator turn fault in induction motor. The sequence current analysis is done for turn fault condition. Various factors influencing the total measured negative sequence current such as unbalanced voltage and inherent asymmetry have been reviewed. To compensate the voltage unbalance and non-idealities in the machine, utilization of measured negative sequence current, impedance, admittance, or semi empirical formula is developed. The output of a well-trained feed forward back propagation neural network classifies the severity of fault level in stator winding. The method of considering the effects of turn faults on inter-turn fault detection improves sensitivity meanwhile reduces the prospect of misdetection.

Comparative study of advanced techniques for the diagnosis of induction motors

This work is a comparative study between the various advanced technologies of diagnosis of induction motors published recently and to make a classification of these diagnostic techniques according to their sensitivities from experimental results of stator short-circuit faults between stator turns. By using the logarithmic FFT spectrum, we can discover the best method to detect faults in their early stages so that we can predict their faults and anticipate breakdowns that can be dangerous for people or the economy.

Research on dynamic simulation technology and fault characteristics of Pumped Storage Power Station

The fault equivalent circuit model of the pumped storage unit is established, the key electrical parameters of the generator motor of the pumped storage power station are analyzed, and the short-circuit fault characteristics of the generator motor of the pumped storage power station are studied. Based on the typical connection mode of pumped storage power station, a dynamic model test platform including dynamic model pumped storage unit, excitation system, frequency conversion starting device and its control system is established. The dynamic model tests of metal or transition resistance short circuit fault, stator ground fault and stator turn to turn short circuit are carried out.

Advanced Control of a Compensator Motor Driving a Variable Speed Diesel Generator with Rotating Stator

Variable speed generators can improve overall genset performance by allowing the diesel engine to reduce its speed at lower loads. In this project, a variable speed diesel generator (VSDG) uses a rotating stator driven by a compensator motor. At lower loads, the stator turns in the opposite direction of the rotor, a process that can be used for purposes like maintaining a fixed relative speed between the two components of a generator. This allows the diesel engine to turn at a lower speed (same as the rotor) and to increase its efficiency. The present research addresses the control of the compensator motor driving the generator’s stator using a variable-frequency drive that adapts the speed to its optimal value according to the load. The performance of the proposed control strategy was tested using a Freescale microcontroller card programmed in C-code to determine the appropriate voltage for the variable-frequency drive. The control algorithm uses a real-time application implemented on an FDRM-KL25Z signal processor board. The control performance of a 2 kW asynchronous motor (LabVolt EMS 8503-00/208 V/3 ϕ/60(50) Hz) was demonstrated experimentally at different operating conditions.

A Novel Stator Turn Fault Detection Technique by Using Equivalent High Frequency Impedance

Stator turn fault is the most serious failure in the electrical machine drive which requires immediate detection techniques. Under such a turn fault, the fundamental change is that the high frequency (HF) impedance of the fault phase is significantly reduced due to the flux nullifying effect of the fault turns. Thus, this paper proposes a novel turn fault detection technique by using the equivalent HF impedance. It is derived by the HF voltage and current signals which are obtained by processing the phase voltages and currents with a bandpass filter. The effectiveness of the proposed is verified by extensive simulation and experimental tests on both surface mounted and interior PM machines. It is demonstrated that the performance of the proposed detection method is superior than the conventional HF current ripple based method. The investigation also confirms that the fault can be detected at an early stage by the proposed method.

On-Line Detection of Stator Faults in DTC-Driven IM Using SC Impedance Matrix Off-Diagonal Term

Stator's turn fault is one of the major causes of induction motor's (IM) failures. IMs are typically driven by direct torque control (DTC) on industry applications and more recently, on electric vehicles. In this article, an in-service nonintrusive stator turn fault detection (FD) technique for a DTC inverter fed IM is proposed. The presented FD strategy is based on the on-line estimation of the off-diagonal term in the IM sequence components (SCs) impedance matrix. The FD does not require prior knowledge of IM's parameters, and it is robust and immune against sensor's inherent errors. Furthermore, the proposed FD routine is able to detect incipient failure of approximately 1% fault severity factor. Two practical methodologies are applied for the computation of the SC: Symmetrical components and Savitzky-Golay filter. Simulation reinforced by experimental results demonstrated the success of the FD in a closed-loop controlled inverter driven IM.

Effective Turn Fault Mitigation by Creating Zero Sequence Current Path for a Triple Redundant 3 × 3-Phase PMA SynRM

Effective mitigation of excessive stator turn fault current is crucial for fault tolerant machine drives. In this paper, a simple and effective method is proposed for a triple redundant 3 × 3-phase permanent magnet-assisted synchronous reluctance machine by using three 3-phase 4-leg inverters. The fourth leg creates a zero sequence current path when a terminal short circuit is applied in an event of a turn fault in a 3-phase winding set. Consequently, the zero sequence flux linkages are reduced by the resultant zero sequence current. This leads to lower residual flux linkage and decreased fault current. The machine drive can therefore have larger safety margin or can be designed for improved torque density and efficiency. The proposed approach is verified by both finite element (FE) simulations and experimental tests in a wide operation range. It shows that the fault current is reduced by ∼40% and the output torque is not affected.

A Discrete Wavelet transform based Protection Scheme for Three Phase Induction Motor

This paper has proposed an approachwhich detects the stator turn to turn faults and phase to ground faults in stator winding of three induction motor. This method proposes analysis of stator winding currents for both normal and fault conditions. High frequency universal model of three phase induction motor used for MATLAB simulation. By using the wavelet MRA technique, the approximate and detailed coefficients of the faulty voltage and current waveforms of the machine are generated under different fault conditions. From the approximate coefficients the type of the fault has been identified. Depending on the energies of the signal the fault diagnosis can be done. The proposed protection scheme is reliable and fast for various fault inception angles.

A Discrete Wavelet transform based Protection Scheme for Three Phase Induction Motor

This paper has proposed an approachwhich detects the stator turn to turn faults and phase to ground faults in stator winding of three induction motor. This method proposes analysis of stator winding currents for both normal and fault conditions. High frequency universal model of three phase induction motor used for MATLAB simulation. By using the wavelet MRA technique, the approximate and detailed coefficients of the faulty voltage and current waveforms of the machine are generated under different fault conditions. From the approximate coefficients the type of the fault has been identified. Depending on the energies of the signal the fault diagnosis can be done. The proposed protection scheme is reliable and fast for various fault inception angles

Detection of Stator Short-Circuit Faults in Induction Motors Using the Concept of Instantaneous Frequency

Because of considerable importance of induction motors in different industries, fault detection of these motors has gained importance in the literature. One of the attractive approaches in this regard is motor current signature analysis. Thanks to simplicity and its lower cost, this method has been preferred compared to the other methods. In this paper, first, a model in which stator turn fault was taken into account is presented. Then, by stator current analysis using empirical mode decomposition (EMD), intrinsic-mode functions of the signals are derived. By selection of the calculated IMF in the first row of the EMD, its instantaneous frequency (IF) is estimated using adaptive IF estimation. Variation of the estimated IF is utilized for detection of different stator turn faults. The method is evaluated using plenty of simulations and some experiments.

Stator Turn Fault Modeling for a Triple Redundant 3 × 3-Phase PMA SynRM

Accurate stator turn fault (STF) modeling technique is of paramount importance to assess the machine fault behavior and develop fault detection and mitigation strategies for a fault-tolerant machine drive system. In this paper, an STF model is proposed for a triple redundant 3 × 3-phase permanent-magnet-assisted synchronous reluctance machine. The effect of turn fault current is represented by equivalent inputs to a general flux linkage model for each three-phase set. Subsequently, the flux linkage of the fault turns is derived according to the coil location and slot position of the fault. The complete model is obtained by combining the flux linkage model with the governing voltage equations. The effectiveness and flexibility of the proposed model have been validated by extensive finite element simulations and experimental tests in various operation conditions. It is demonstrated that the model can predict the machine behavior with and without the mitigation action in the form of terminal short circuit.

Induction Motor Faults Diagnosis when Considering Bars Skew and Saturation Effects

The objective of the work presented in this paper is the diagnosis of the three-phase induction machine with secondary effects such as the rotor bars skewing and the saturation phenomenon. To enable reliable diagnosis of an induction machine, a mathematical model is required to simulate the machine behavior. Among the existing mathematical models, the approach of the winding function is the most promising because it takes into account the actual distribution of the windings in the stator slots. Nevertheless, the major drawback of this model is the non-consideration of the skewing effect of the bars and the non-linear evolution of the FMM between the ends of the slots. The aim of this paper is to use the modified winding function approach (MWFA) with 2D extension to take into account the rotor bars skewing and saturation effects in the presence of faults such as the rotor broken bars, the short-circuit between stator turns and the eccentricity. A series of simulations is conducted to study the spectral contents of the stator current of the induction squirrel cage motor in the various operating cases.

Permanent-Magnet Machine Flux and Torque Response Under the Influence of Turn Fault

This paper analyzes different stator windings configurations for permanent-magnet synchronous machines during the presence of a stator turn fault. Due to the inverter pulsewidth modulation, the fault commonly occurs in variable-frequency permanent-magnet machine drives. In this paper, two types of windings are compared to identify key machine topologies that can achieve the reduced influence of the turn fault. When the machine is operated in real time, the windings with separated neutral points reduce the torque ripple caused by fault-reflected flux harmonics. Analytical models based on equivalent circuits are developed to predict the machine flux and torque waveform during the presence of the turn fault. All developed analytical models are verified by the finite-element analysis and experimental results on a 750-W surface permanent-magnet machine prototype.

Stator Turn Fault Detection by Second Harmonic in Instantaneous Power for a Triple-Redundant Fault-Tolerant PM Drive

Fast and reliable detection of stator faults is of key importance for fail-safe and fault-tolerant machine drives in order to immediately trigger appropriate fault mitigation actions. The paper presents a detailed analytical and experimental analysis of the behavior of a closed-loop controlled permanent magnet machine drive under interturn fault conditions. It is shown that significant second harmonic components in the dq voltages, currents, instantaneous active power (IAP), and instantaneous reactive power (IRP) are generated during turn fault conditions. The analyses further show that the increase of the second harmonic in IAP and IRP during fault conditions is comparatively higher than that of voltage and current, making them ideal candidates as turn fault indicators. A turn fault detection technique based on second harmonic in IAP and IRP is implemented and demonstrated for a triple-redundant, fault-tolerant permanent magnet assisted synchronous reluctance machine drive. The effectiveness of the proposed detection technique over the whole operation region is assessed, demonstrating fast and reliable detection over most of the operating region under both motoring and generating mode.

Fault Detection and Tolerant Capability of Parallel-Connected Permanent Magnet Machines Under Stator Turn Fault

This paper analyzes the influence of stator windings turn-to-turn fault on inverter-fed permanent magnet (PM) machines. By adding a secondary neutral point (NP) in stator windings, the turn fault detection and tolerant capability can all improve considering a small turn-to-turn short at an early stage. From the perspective on fault detection, the proposed windings with two NPs increase the equipment impedance per NP. Once a turn fault occurs, the fault-induced voltage harmonic magnitude increases. It results in a better signal-to-noise ratio for the fault detection. From the perspective on tolerant drive, the fault-induced circulating currents can flow across different phase coils in the windings with two NPs. Reduced effect on circulating currents in a faulty machine is achieved due to the current diversion. Turn fault induced additional losses are then decreased compared to conventional windings with only one NP. A 1-kW PM machine with two different windings is tested to verify the fault detection and tolerant performance.

Three Phase Induction Motor's Stator Turns Fault Analysis Based on Artificial Intelligence

This article presents a method for fault detection and diagnosis of stator inter-turn short circuit in three phase induction machines. The technique is based on modelling the motor in the dq frame for both health and fault cases to facilitate recognition of motor current. Using an Adaptive Neuro-Fuzzy Inference System (ANFIS) to provide an efficient fault diagnosis tool. An artificial intelligence network determines the fault severity values using the stator current history. The performance of the developed fault analysis method is investigated using Matlab/Simulink® software. Stator turns faults are detected through current monitoring of a 2 Hp three phase induction motor under various loading conditions. Fault history is calculated under various loading conditions, and a wide range of fault severity.

A Simplified Frequency-Domain Detection of Stator Turn Fault in Squirrel-Cage Induction Motors Using an Observer Coil Technique

This paper presents the distinct advantages of stator fault detection using a novel radial flux sensing technique. Intensive research efforts in the past have been focused on the flux signature analysis as they have been more efficient compared to classical motor current signature analysis. In this paper, it is observed that a flux sensing simple internal observer coil (OC) is more succinct than external flux sensors. The proposed simplified, inexpensive technique has yet not been reported in the literature. The new results of root mean square (RMS), fundamental, third harmonic, and total harmonic distortion analysis of the voltage spectra of the OCs are found to exhibit variations in relation to the severity of interturn faults as compared to the healthy condition. The mathematical theory of the technique is provided and supported by an experimental validation. An experiment for confirming the performance of the proposed method was done on a 2.2-kW three-phase four-poles, 440-V squirrel-cage induction motor, increasing the fault level in steps from 1% to 15% combined with variations in load from no load to full load.