Showing papers on "Induction motor published in 2013"
TL;DR: A novel diagnostic algorithm that allows the real-time detection and localization of multiple power switch open-circuit faults in inverter-fed ac motor drives and its robustness against false alarms is presented.
Abstract: Three-phase inverters are currently utilized in an enormous variety of industrial applications, including variable-speed ac drives. However, due to their complexity and exposure to several stresses, they are prone to suffer critical failures. Accordingly, this paper presents a novel diagnostic algorithm that allows the real-time detection and localization of multiple power switch open-circuit faults in inverter-fed ac motor drives. The proposed method is quite simple and just requires the measured motor phase currents and their corresponding reference signals, already available from the main control system, therefore avoiding the use of additional sensors and hardware. Several experimental results using a vector-controlled permanent-magnet synchronous motor drive are presented, showing the diagnostic algorithm effectiveness, its relatively fast detection time, and its robustness against false alarms.
323 citations
04 Nov 2013
TL;DR: In this paper, the efficiency analysis on the best available electric motors and emerging motor technologies, such as axial-flux permanent-magnet synchronous motors, is presented, as well as a study on the theoretical efficiency limit achievable taking into account those existing design options.
Abstract: Premium (IEC IE3 Class) efficiency Motors are now mandatory in North America. Super-Premium (IEC IE4 Class) and IE5 Ultra-Premium efficiency classes are defined in the second edition of Standard IEC 60034-30. For line-start fixed-speed applications, Super-Premium IE4-Class Line-Start Permanent-Magnet Motors and Squirrel-Cage Induction Motors are recent entrances in the industrial motor market. For variable-speed applications, IE4-Class Variable-Reluctance Synchronous Motors are also a recent entrance in the market. For the low power range, moving from IE4 to IE5 class, may require moving away from radial-flux induction motor technology, into to the permanent magnet and reluctance technology, either using Rare-Earth or Ferrite magnets. In this paper, efficiency analysis on the best available electric motors and emerging motor technologies, such as axial-flux permanent-magnet synchronous motors, is presented. The potential efficiency gain associated with several design options as well as a study on the theoretical efficiency limit achievable taking into account those existing design options are described.
294 citations
27 Nov 2013
TL;DR: In this article, a study of postfault control for an asymmetrical six-phase induction machine with single and two isolated neutral points, during a single open-phase fault is presented.
Abstract: The paper presents a study of postfault control for an asymmetrical six-phase induction machine with single and two isolated neutral points, during single open-phase fault. Postfault control is based on the normal decoupling (Clarke) transformation, so that reconfiguration of the controller is minimized. Effect of the single open-phase fault on the machine equations under this control structure is discussed. Different modes of postfault operation are analyzed and are further compared in terms of the achievable torque and stator winding losses. Validity of the analysis is verified using experimental results obtained from a six-phase induction motor drive prototype.
286 citations
TL;DR: A new approach for fault detection and diagnosis of IMs using signal-based method based on signal processing and an unsupervised classification technique called the artificial ant clustering is described, which proves the efficiency of the approach compared with supervised classification methods in condition monitoring of electrical machines.
Abstract: The presence of electrical and mechanical faults in the induction motors (IMs) can be detected by analysis of the stator current spectrum. However, when an IM is fed by a frequency converter, the spectral analysis of stator current signal becomes difficult. For this reason, the monitoring must depend on multiple signatures in order to reduce the effect of harmonic disturbance on the motor-phase current. The aim of this paper is the description of a new approach for fault detection and diagnosis of IMs using signal-based method. It is based on signal processing and an unsupervised classification technique called the artificial ant clustering. The proposed approach is tested on a squirrel-cage IM of 5.5 kW in order to detect broken rotor bars and bearing failure at different load levels. The experimental results prove the efficiency of our approach compared with supervised classification methods in condition monitoring of electrical machines.
232 citations
TL;DR: In this article, a speed observation scheme using artificial neural network (ANN) inverse method was proposed to effectively reject the influence of speed detection on system stability and precision for a bearingless induction motor.
Abstract: To effectively reject the influence of speed detection on system stability and precision for a bearingless induction motor, this paper proposes a novel speed observation scheme using artificial neural network (ANN) inverse method. The inherent subsystem consisting of speed and torque winding currents is modeled, and then its inversion is implemented by the ANN. The speed is successfully observed via cascading the original subsystem with its inversion. The observed speed is fed back in the speed control loop, and thus, the speed-sensorless vector drive is realized. The effectiveness of this proposed strategy has been demonstrated by experimental results.
220 citations
TL;DR: A three-phase cascaded multilevel inverter that uses five-level transistor-clamped H-bridge power cells that provides higher output quality with relatively lower power loss as compared to the other conventional inverters with the same output quality.
Abstract: This paper presents a three-phase cascaded multilevel inverter that uses five-level transistor-clamped H-bridge power cells. Multicarrier phase-shifted pulse-width modulation method is used to achieve balanced power distribution among the power cells. A new method to balance the midpoint capacitor voltage in each cell is developed and tested. The analysis of the output voltage harmonics and the total power losses covering the conduction and the switching power losses are carried out and compared with the cascaded neutral-point-clamped and the conventional cascaded H-bridge inverters. For verifications, the proposed inverter is experimentally tested on an induction motor. From the results, the proposed inverter provides higher output quality with relatively lower power loss as compared to the other conventional inverters with the same output quality.
179 citations
TL;DR: Experimental results obtained from induction motors show that the proposed diagnosis algorithm is capable of detecting BRB faults with an accuracy that is superior to the zoom-based MUSIC algorithm.
Abstract: The classical multiple signal classification (MUSIC) method has been widely used in induction machine fault detection and diagnosis. This method can extract meaningful frequencies but cannot give accurate amplitude information of fault harmonics. In this paper, we propose a new frequency analysis of stator current to estimate fault-sensitive frequencies and their amplitudes for broken rotor bars (BRBs). The proposed method employs a frequency estimator, an amplitude estimator, and a fault decision module. The frequency estimator is implemented by a zoom technique and a high-resolution analysis technique known as the estimation of signal parameters via rotational invariance techniques, which can extract frequencies accurately. For the amplitude estimator, a least squares estimator is derived to obtain amplitudes of fault harmonics, without frequency leakage. In the fault decision module, the fault diagnosis index from the amplitude estimator is used depending on the load conditions of the induction motors. The fault index and corresponding threshold are optimized by using the false alarm and detection probabilities. Experimental results obtained from induction motors show that the proposed diagnosis algorithm is capable of detecting BRB faults with an accuracy that is superior to the zoom-based MUSIC algorithm.
152 citations
TL;DR: A new control system, based on field programmable gate array technology, targeting the powertrain control of multi-motor electric vehicles (EVs), and demonstrates a good slip regulation and robustness to disturbances.
Abstract: This paper presents a new control system, based on field programmable gate array technology, targeting the powertrain control of multi-motor electric vehicles (EVs) The control chip builds around a reusable intellectual property core named propulsion control unit, which features motor control functions with field-orientation methods, and energy loss minimization of induction motors In order to improve the EV safety, the control system was extended with a wheel slip controller based on the sliding mode framework The robustness to parametric and modeling uncertainties is the main attraction in this design, thanks to a simple connection that was found between the driving torque request and the model uncertainty To overcome the chattering issue, which arrives from the discontinuous nature of the sliding control, the conditional integrator approach was employed, enabling a smooth transition to a Proportional+Integral control law, with anti-windup, when the tire slip is close to the setpoint The controller asymptotic stability and robustness was analytically investigated through the Lyapunov method Experimental results, obtained with a multi-motor EV prototype under low grip conditions, demonstrate a good slip regulation and robustness to disturbances
151 citations
TL;DR: The model is validated by experiments, owing to a dedicated test setup, where an external vibration source was employed, together with ball bearing alterations in order to decrease the stiffness of the support along the radial direction.
Abstract: This paper investigates the relationship between vibration and current in induction motors operated under external vibrations Two approaches are usually available to define this relationship The former is based on airgap variations, while the latter is based on torque perturbation This paper is focused on the airgap variation model The ball bearing fault is modeled by contact mechanics External vibrations often occur in many industrial applications where externally induced vibrations of suitable amplitude cause cyclic radial loading on the machine shaft The model is validated by experiments, owing to a dedicated test setup, where an external vibration source (shaker) was employed, together with ball bearing alterations in order to decrease the stiffness of the support along the radial direction To maximize the effects of externally induced vibrations, the frequency chosen was near the flexural resonance of the rotor (determined by finite-element method analysis) The direction of the external vibration is radial with respect to the axis of the electric machine under test During tests, both stator phase currents and vibration of the machine were sampled The test setup allowed one to vary the machine speed and load, vibration amplitude, and bearing stiffness (damage level) Radial effects are usually visible only in the case of large failures that result in significant airgap variations, as confirmed by experiments
148 citations
TL;DR: The novelty of the presented solution is the integration of a simple observer for both speed/flux and current control purposes, and the obtained results have been improved in comparison to the previous works.
Abstract: Today, speed sensorless modes of operation are becoming standard solutions in the area of electric drives. This paper presents a speed sensorless control system of an induction motor with a predictive current controller. A closed-loop estimation system with robustness against motor parameter variation is used for the control approach. The proposed algorithm has been implemented using field-programmable gate arrays (FPGAs) and a floating-point digital signal processor (DSP). Both computational elements have been integrated on a single board SH65L type and interfaced to the power electronic converter, and the use of proper FPGA and DSP optimizes the cost and computational properties. The novelty of the presented solution is the integration of a simple observer for both speed/flux and current control purposes, and the obtained results have been improved in comparison to the previous works. An overview of the test bench consisting of a digital control board, as well as computational algorithms and system benchmarks, is presented. All the tests were performed experimentally for 5.5-kW electric drives.
143 citations
TL;DR: This work presents the design and implementation of a low-cost SoC design that utilizes reconfigurable hardware and a customized embedded processor for time-frequency analysis on industrial equipment through short-time Fourier transform and discrete wavelet transform.
Abstract: Nowadays industry pays much attention to prevent failures that may interrupt production with severe consequences in cost, product quality, and safety. The most-analyzed parameters for monitoring dynamic characteristics and ensuring correct functioning of systems are electric current, voltage, and vibrations. System-on-chip (SoC) design is an approach to increase performance and overcome costs during equipment monitoring. This work presents the design and implementation of a low-cost SoC design that utilizes reconfigurable hardware and a customized embedded processor for time-frequency analysis on industrial equipment through short-time Fourier transform and discrete wavelet transform. Three study cases (electric current supply to an induction motor during startup transient, voltage supply to an induction motor through a variable speed drive, and vibration signals from industrial-robot links) show the suitability of the proposed monitoring system for time-frequency analysis of different signals in distinct industrial applications, and early diagnosis and prognosis of abnormalities in monitored systems.
TL;DR: In this article, an improved Hilbert method was proposed by conjugating the Hilbert transform and ESPRIT together to detect rotor bar faults in induction motors, where the estimation of signal parameters via rotational invariance technique (ESPRIT) was introduced to replace FFT.
Abstract: The traditional Hilbert method to detect broken rotor bar fault in induction motors is reviewed and its major drawbacks are clearly revealed, namely, deteriorating or even completely failing when a motor operating at low slip due to the fixed constraints of fast Fourier transform (FFT) is used in this method. To overcome this, the estimation of signal parameters via rotational invariance technique (ESPRIT) is then introduced to replace FFT, and an improved Hilbert method is thus presented by conjugating the Hilbert transform and ESPRIT together. Experimental results of a small motor in a laboratory and a large motor operating on an industrial site are reported to demonstrate the effectiveness of the improved Hilbert method.
TL;DR: The transient as well as the steady-state performance of the proposed nine-level inverter-fed IM drive system is experimentally verified in the entire modulation range including the overmodulation region.
Abstract: A new scheme for nine-level voltage space-vector generation for medium-voltage induction motor (IM) drives with open-end stator winding is presented in this paper. The proposed nine-level power converter topology consists of two conventional three-phase two-level voltage source inverters powered by isolated dc sources and six floating-capacitor-connected $H$ -bridges. The $H$ -bridge capacitor voltages are effectively maintained at the required asymmetrical levels by employing a space vector modulation (SVPWM) based control strategy. An interesting feature of this topology is its ability to function in five- or three-level mode, in the entire modulation range, at full-power rating, in the event of any failure in the $H$ -bridges. This feature significantly improves the reliability of the proposed drive system. Each leg of the three-phase two-level inverters used in this topology switches only for a half cycle of the reference voltage waveform. Hence, the effective switching frequency is reduced by half, resulting in switching loss reduction in high-voltage devices. The transient as well as the steady-state performance of the proposed nine-level inverter-fed IM drive system is experimentally verified in the entire modulation range including the overmodulation region.
TL;DR: It is shown that the performance of the PWM techniques is very similar and that one CBPWM and one SVPWM technique are characterised with identical performance, however, using the algorithm complexity as the main criterion, space vector techniques are more involved.
Abstract: Multilevel inverter supplied multiphase variable-speed drive systems have in recent times started attracting more attention, due to various advantages that they offer when compared to the standard three-phase two-level drives. For proper functioning of such systems good pulsewidth modulation (PWM) strategy is of crucial importance. Control complexity of multiphase multilevel inverters increases rapidly with an increase in the number of phases and the number of levels. This paper deals with a three-level neutral point clamped (NPC) inverter supplied five-phase induction motor drive and analyses five PWM strategies: three are carrier-based (CBPWM) and two are space vector based (SVPWM). The aim is to provide a detailed comparison and thus conclude on pros and cons of each solution, providing a guideline for the selection of the most appropriate PWM technique. Experimental results are provided for all analysed PWM methods. The comparison of the PWM techniques is given in terms of the voltage and current waveforms and spectra, as well as the total harmonic distortion (THD) in a whole linear modulation index range, which is used as the global figure of merit. Properties of the common mode voltage (CMV) are also investigated. Complexity of the algorithms, in terms of the computational time requirements and memory consumption, is addressed as well. It is shown that the performance of the PWM techniques is very similar and that one CBPWM and one SVPWM technique are characterised with identical performance. However, using the algorithm complexity as the main criterion, space vector techniques are more involved.
TL;DR: A method based on the nonlinear dynamical system state observability theory is proposed, resulting in a unified approach to the ac drive observability analysis.
Abstract: AC induction motors and permanent magnet synchronous drives became very popular for motion control applications due to their simple and reliable construction. Sensorless drive control is required in many applications to reduce drive production costs. While many approaches to magnetic flux, rotor speed, or other quantities needed to control electrical machine were proposed, conditions under which these quantities can be estimated are not often sufficiently investigated. In this paper, induction machine and permanent-magnet-synchronous-machine drive state observability analysis is presented, together with conditions allowing reliable rotor speed and position estimation. A method based on the nonlinear dynamical system state observability theory is proposed, resulting in a unified approach to the ac drive observability analysis.
TL;DR: In this article, the performance of a dual 2-level inverter feeding an open-end winding induction motor drive is investigated and a current trajectory is theoretically obtained directly from the switching states of the dual inverter in a stationary reference frame.
Abstract: This paper presents investigations on current ripple in a dual 2-level inverter feeding an open-end winding induction motor drive. Pulsewidth modulations (PWMs) for the independently controlled inverters are implemented using a simple effective time placement affected by offset-time concept, thus, eliminating the use of sector identification and lookup tables. Analytical expressions for ripple content in the motor phase current are developed and a current trajectory is theoretically obtained directly from the switching states of the dual inverter in a stationary reference frame. In addition, this paper also describes a current ripple trajectory in the motor by exploring the freedom of independently operating the individual inverters with different PWMs. Based on the analysis, discontinuous PWMs are employed for the individually inverters that not only offer the advantage of reducing the total switching commutations in the inverters but also reduces the current ripple. Analytical expression for the RMS ripple current and variation in RMS ripple current in one cycle of operation for different PWMs are also presented for the entire speed range of the dual-inverter drive. The performance of the dual-inverter drive with the proposed PWM variants is first studied analytically and then verified by performing suitable experiments on a 1-kW open-end winding induction motor drive.
TL;DR: In this paper, the authors highlight the sensorless estimation techniques applied to the IM-VFDs for sustainable reliability and energy savings for critical applications such as electric vehicles, high performance machine tools, fans, compressors, etc.
Abstract: Variable frequency drives (VFDs) can provide reliable dynamic systems and significant savings in energy usage and costs of the induction motors (IMs). Sensorless controlled IM drives have advantages in terms of efficiency enhancement and energy savings for critical applications such as electric vehicles, high performance machine tools, fans, compressors, etc. IM drives without having speed sensors or optical encoders mounted at the motor shaft are attractive because of their lower cost and higher reliability. When mechanical speed sensor is removed, the rotor speed information is estimated using the measured quantities of stator voltages and currents at the IM terminals. This paper highlights the sensorless techniques applied to the IM drives for sustainable reliability and energy savings. Overview on the IM mathematical model is briefly summarized to establish a physical basis for the sensorless schemes used. Further, the different types of IM-VFDs are presented in the paper. The main focus of this review is on the sensorless estimation techniques which are being applied to make IM-VFDs more effective during wide speed operations including very-high and very-low speed regions.
TL;DR: It is shown that the steady-state performance of MPDxC and FMCC is similar when the switching horizon of MPdxC is limited, however, when the switched horizon is extended, the performance ofMPD xC is shown to be superior to FMCC, the horizon of which is inherently restricted.
Abstract: In medium-voltage (MV) drives, the switching frequency is limited to a few hundred Hz, for which high-performance control and modulation schemes are necessary to maintain acceptable current and torque distortion. Forced machine current control (FMCC) is a predictive control strategy for MV drives which was proposed in the early 1980s, which can be formulated for either torque or current control. Recently, model predictive direct torque control (MPDTC) and model predictive direct current control (MPDCC) have been developed, sharing with FMCC the use of hysteresis bounds, switching and prediction horizons. However, the relative performances of these schemes are yet to be compared. Through simulation, this paper compares the schemes across a range of operating points. It is shown that the steady-state performance of MPDxC and FMCC is similar when the switching horizon of MPDxC is limited. However, when the switching horizon is extended, the performance of MPDxC is shown to be superior to FMCC, the horizon of which is inherently restricted.
TL;DR: The objective of this paper is to make a clear and rigorous characterization and classification of the harmonics present in a healthy cage rotor induction motor spectrum as a starting point for diagnosis.
Abstract: Before applying current-signature-analysis-based monitoring methods, it is necessary to thoroughly analyze the existence of the various harmonics on healthy machines. As such an analysis is only done in very few papers, the objective of this paper is to make a clear and rigorous characterization and classification of the harmonics present in a healthy cage rotor induction motor spectrum as a starting point for diagnosis. Magnetomotive force space harmonics, slot permeance harmonics, and saturation of main magnetic flux path through the virtual air-gap permeance variation are taken into analytical consideration. General rules are introduced giving a connection between the number of stator slots, rotor bars, and pole pairs and the existence of rotor slot harmonics as well as saturation-related harmonics in the current spectrum. For certain combinations of stator and rotor slots, saturation-related harmonics are shown to be most prominent in motors with a pole pair number of two or more. A comparison of predicted and measured current harmonics is given for several motors with different numbers of pole pairs, stator slots, and rotor bars.
TL;DR: The experimental results for V/F control of 3-Phase induction motor using GSM clearly shows constant volts per hertz and stable inverter line to line output voltage.
Abstract: This paper presents design and analysis of a three phase induction motor drive using IGBT‟s at the inverter power stage with volts hertz control (V/F) in closed loop using a microcontroller. A 1HP, 3-phase, 415V, 50Hz induction motor is used as load for the inverter. Oscilloscope is used to record and analyze the various waveforms. The experimental results for V/F control of 3-Phase induction motor using GSM clearly shows constant volts per hertz and stable inverter line to line output voltage.
TL;DR: In this paper, the authors proposed a direct torque control (DTC) strategy for induction motor (IM) drives fed by a four-switch three-phase inverter (FSTPI).
Abstract: This paper proposes a novel direct torque control (DTC) strategy for induction motor (IM) drives fed by a four-switch three-phase inverter (FSTPI). The introduced strategy is based on the emulation of the operation of the conventional six-switch three-phase inverter (SSTPI). This has been achieved thanks to a suitable combination of the four unbalanced voltage vectors intrinsically generated by the FSTPI, leading to the synthesis of the six balanced voltage vectors of the SSTPI. This approach has been adopted in the design of the vector selection table of the proposed DTC strategy which considers a subdivision of the Clarke plane into six sectors. Simulation results have revealed that, thanks to the proposed DTC strategy, FSTPI-fed IM drives exhibit interesting performance. These have been experimentally validated and compared to the ones yielded by the Takahashi and the basic DTC strategies dedicated to the SSTPI and to the FSTPI, respectively.
TL;DR: In this article, a modified spoke-type FMM with a novel rotor configuration was presented for a traction motor of low-speed EVs, and the characteristics of the modified FMM were numerically compared with a conventional FMM at the same design condition.
Abstract: Rare-earth magnets have been widely employed for traction drive motors of hybrid and electric vehicles (EVs) due to high energy density. Nevertheless, the magnets have critical problems such as unstable supply and high cost. Recently, in order to solve the problems, a variety of motors not using rare-earth materials have been reviewed, such as an induction motor, a switched reluctance motor, and a spoke-type ferrite magnet motor (FMM). In this paper, a modified spoke-type FMM with a novel rotor configuration was presented for a traction motor of low-speed EVs. The characteristics of the modified spoke-type FMM are numerically compared with a conventional spoke-type FMM at the same design condition. Finally, the modified spoke-type FMM is fabricated and tested in order to verify its performance and feasibility.
11 Mar 2013
TL;DR: An overview of typical failure mechanisms and their causes is presented in this article, where recent advances and future perspectives are discussed as well as important and fundamental papers are reviewed and reported in a comprehensive list of references.
Abstract: This paper investigates diagnostic techniques for electrical machines with special reference to rotor faults in induction motors. An overview of typical failure mechanisms and their causes is presented. Also recent advances and future perspectives are discussed. To this aim the most recent related works along with important and fundamental papers are reviewed and reported in a comprehensive list of references.
TL;DR: In this article, the optimal amount and locations for installing dynamic reactive resources are found by control vector parameterization (CVP), a dynamic optimization approach, by utilizing results from trajectory sensitivity analysis, singular value decomposition and linear programming optimization.
Abstract: Short term voltage stability poses a significant threat to system stability and reliability. This paper applies dynamic VAr injection to ensure short term voltage stability following a large disturbance in a power system with high concentration of induction motor loads. Decelerating and stalling of induction motor loads is considered to be the major cause of fault induced delayed voltage recovery (FIDVR) and short term voltage stability. If system dynamics are not taken into account properly, the proposed control solution may be an expensive over design or an under design that is not capable of eliminating FIDVR problems completely. In this work, the optimal amount and locations for installing dynamic reactive resources are found by control vector parameterization (CVP), a dynamic optimization approach. The efficiency and effectiveness of this approach is improved by utilizing results from trajectory sensitivity analysis, singular value decomposition and linear programming optimization. Dynamic optimization based on CVP approach is tested in an IEEE 162-bus system and a realistic large scale utility power system.
TL;DR: In this article, a study of the influences of the broken rotor bar fault to the electromagnetic characteristics of the induction motor is presented, using an asynchronous cage motor and finite element method analysis.
Abstract: The cracked or broken bar fault constitutes about 5-10% of total induction motor failures and leads to malfunction as well as reduction of the motor's life cycle. This is the reason why there is continuous research on techniques for prompt detection. In this study, a study of the influences of the broken bar fault to the electromagnetic characteristics of the induction motor is presented, using an asynchronous cage motor and finite element method analysis. To this direction, two models have been created and studied: a healthy and one with a broken bar. Additionally, a new approach on the detection of the broken rotor bar fault through the electromagnetic torque monitoring is suggested and validated through experimental results.
TL;DR: In this paper, the impact of the geometry of a permanent magnet motor on the capability to detect the rotor position without sensors by means of a high-frequency signal injection was investigated, which is characterized by a magnetic saliency, necessary for the sensorless rotor position detection.
Abstract: This paper investigates the impact of the geometry of a permanent-magnet (PM) motor on the capability to detect the rotor position without sensors by means of a high-frequency signal injection. An interior PM motor with three rotor flux barriers is considered, which is characterized by a magnetic saliency, necessary for the sensorless rotor position detection. The objective is twofold: 1) to keep an adequate saliency in all the operating range of the motor, including operations at high current, and 2) to limit the angular error of the rotor detection, which is due to the effect of the cross-saturation between the d- and the q-axes. The phenomenon of iron saturation is deeply analyzed, highlighting how the saturation of both the stator and rotor affects the machine performance, in terms of sensorless rotor position detection capability. To this purpose, the motor geometry is modified so as to achieve a higher iron saturation in the stator and, then, in the rotor. Then, the volume of the PM is changed so as to emphasize the impact of the PM flux. Different rotor geometries are finally compared with the initial one.
TL;DR: New expressions of symmetrical components of the stator currents of the induction motor (IM) in steady state and under different stator faults, useful to ensure an efficient fault diagnosis are proposed.
Abstract: This paper proposes new expressions of symmetrical components (SCs) of the stator currents of the induction motor (IM) in steady state and under different stator faults, useful to ensure an efficient fault diagnosis. In this paper, the considered stator faults are interturns short circuit, phase-to-phase, and single-phase-to-ground faults. An analytical study of the behavior of these expressions shows that, under balanced supply voltage, the phase angle and the magnitude of the negative- and zero-sequence currents can be considered as reliable indicators of stator faults of the IM. The behavior of the developed expressions of the SCs is also verified experimentally on a 1.1-kW IM under different fault conditions, different frequencies, and different load conditions. The good agreement between the analytical and experimental values leads to consider the negative- and zero-sequence currents as powerful and effective indicators of stator faults.
TL;DR: In this article, a new method for demodulating the stator current prior to its spectral analysis is proposed, using the Teager-Kaiser energy operator, which is able to remove the mains component of the current with an extremely low usage of computer resources.
Abstract: The diagnosis of induction motors through the spectral analysis of the stator current allows for the online identification of different types of faults. One of the major difficulties of this method is the strong influence of the mains component of the current, whose leakage can hide fault harmonics, especially when the machine is working at very low slip. In this paper, a new method for demodulating the stator current prior to its spectral analysis is proposed, using the Teager-Kaiser energy operator. This method is able to remove the mains component of the current with an extremely low usage of computer resources, because it operates just on three consecutive samples of the current. Besides, this operator is also capable of increasing the signal-to-noise ratio of the spectrum, sharpening the spectral peaks that reveal the presence of the faults. The proposed method has been deployed to a PC-based offline diagnosis system and tested on commercial induction motors with broken bars, mixed eccentricity, and single-point bearing faults. The diagnostic results are compared with those obtained through the conventional motor current signature analysis method.
TL;DR: A simple, new active damping technique is presented that can stabilize effectively the drive system at unstable operating points, offering greatly reduced input line current total harmonic distortion.
Abstract: A small dc-link capacitor based drive system shows instability when it is operated with large input line inductance at operating points with high power. This paper presents a simple, new active damping technique that can stabilize effectively the drive system at unstable operating points, offering greatly reduced input line current total harmonic distortion. The proposed method requires only a first-order, high-pass filter with a gain. Active damping voltage terms, linked directly to the dc-link voltage ripple through gain units, are injected to the drive machine for stabilizing the operating points. The stabilizing effect of the active damping terms is demonstrated for an induction machine based drive system. The effects of the added damping terms on the machine current and dc-link voltage are analyzed in detail. A design recommendation for the proposed active damping terms is given. Experimental results verifying the effectiveness of the new active damping method are presented.
TL;DR: Two analytical approaches are proposed in this paper to predict the current trajectory and the ripple content in the drive system to limit the switching power loss to a single VSI at all instants and also reduce the switching commutations in the dual VSI by 50%.
Abstract: A dual two-level voltage source inverter (VSI) can synthesize a three-level voltage space vector employing an open-end winding induction motor. Space-vector-based pulsewidth modulation (PWM) variants for this dual VSI are proposed in this paper that offer the dual advantage of limiting the switching power loss to a single VSI at all instants and also reducing the switching commutations in the dual VSI by 50%. The influence of different error volt seconds (affected with different PWM variants) on the motor phase current in the dual VSI is critically analyzed. To this end, two analytical approaches (one using error-voltage trajectory information and the other using switching state information of the dual VSI) are also proposed in this paper to predict the current trajectory and the ripple content in the drive system. Expressions for rms ripple current are developed with different PWM variants. The efficacy of the proposed analytical approaches to predict the current trajectory and the ripple content is confirmed from the experimental results. All the PWM variants are first simulated using MATLAB and verified experimentally by conducting tests on a three-phase open-end winding induction motor drive controlled with volts per hertz control. The implementation of the PWM algorithms only requires instantaneous magnitudes of three-phase reference voltages and completely avoids the sector identification and lookup tables.