Behavior Of Induction Machine Research Articles

An improved predictive current control for IM drives

In Finite Control Set-Model Predictive Control (FCS-MPC), the model of the induction machine (IM) is expressed in the α-β or d-q reference frame, and then the back-EMF is estimated based on the applied voltage vectors. In this work, the d-q reference frame is used but unlike the existing method, the estimated back-EMF is calculated by filtering the voltage vectors. Moreover, the work studies the importance of the discretization method on the predictive control behavior of IM. It has been demonstrated that the mentioned enhancements lead to an efficient Total Harmonic Distortion value for stator current (THDi) and torque ripple reduction compared to the conventional methods. The proposed Predictive Current Controller (PCC) has been validated experimentally by using a commercial IM of 7.5[kW] controlled by a dSpace 1103 real-time control board running with sample frequencies from 10[kHz]to 80[kHz]. The test results validate the developed controller’s ability to meet the control objectives in a whole range of speeds, loads, and sampling frequencies.

An accurate inter-turn short circuit faults model dedicated to induction motors

Safety, disponibility and continuity of industrial systems are major issue in maintenance. In the last decades, these points are the important axes in the field of research. In fact, in many industrial processes research has picked up a fervent place and a particular importance in the area of fault diagnosis of electrical machines, in fact, a fault prognosis has become almost indispensable. The need of a mathematical model of three-phase induction machine, suitable for the simulation of machines behaviour under fault conditions, has received considerable attention. The paper presents a new practical and more precise model for induction motors after introducing inter turn short circuits faults. The proposed model is based on coupled magnetic circuit theory, capable to take into account any electrical asymmetry conditions. To verify the exactitude and the effectiveness of the model, simulation results for induction machine under interturn short circuit fault are presented. In spite of its simplicity, the proposed model is able to provide useful indications for diagnostic purposes. Experimental study is presented at the end of the paper to show that the proposed model predicts the induction machine behavior with a good accuracy.

Dependency of Machine Efficiency on the Thermal Behavior of Induction Machines

The consideration of the thermal behavior of electric machines is becoming increasingly important in the machine design for electric vehicles due to the adaptation to more dynamic operating points compared to stationary applications. Whereas, the dependency of machine efficiency on thermal behavior is caused due to the impact of temperature on the resulting loss types. This leads to a shift of efficiency areas in the efficiency diagram of electric machines and has a significant impact on the maximum load capability and an impact on the cycle efficiency during operation, resulting in a reduction in the overall range of the electric vehicle. Therefore, this article aims at analyzing the thermal load limits of induction machines in regard to actual operation using measured driving data of battery electric vehicles. For this, a thermal model is implemented using MATLAB® and investigations to the sensitivity of model parameters as well as analysis of the continuous load capacity, thermal load and efficiency in driving cycles under changing boundary conditions are conducted.

Asynchronous machine vector control: PIα controllers for current loops

This article deals with field-oriented control of induction machine squirrel cage. A robust fractional-order controller is applied and investigated to control the induction machine currents isd and isq. The fractional-order gives better fit in regulation operation. For this purpose, this controller form is recommended, especially in industrial systems, thanks to his flexibility, robustness and efficiency to solve complex problems such as electrical parameters changes (i.e. uncertain parameter) caused by the temperature effect. Based on frequency specification and several constraints, the fractional-order controller is designed. The fmincon toolbox optimization is used to adjust ki, kp and α values. In order to show the reliability of the developed controller in the induction machine behavior, several simulation results are carried out and illustrated.

Detecting of Multi Phase Inter Turn Short Circuit in the Five Permanent Magnet Synchronous Motor

Abstract This paper proposes a general model of five phase permanent magnet synchronous machine (PMSM) which is capable of representing the multiphase Inter Turn Short Circuit (ITSC) occurring in several phase simultaneously this model is based on a coupled magnetic circuit approach leading to a differential equations system goveming the induction machine behavior. The obtained time-differential state equations system is implemented under Matlab environment and numerically solved using the fourth order Rung-Kutta method with variable step time corrected at each rotor displacement through the electromagnetic torque. Also, Fast Fourier Transform and (FFT) analysis is performed to the phase current signal to detect the frequency spectrum, Power Spectral Density (PSD) is chosen as a classification method. Its efficiency depends on its ability to discriminate between various faults generating the same range of harmonics in the stator current spectrum and on its ability to evaluate the fault severity. So, in order to improve the efficiency of these diagnosis methods, one needs a relatively accurate model to simulate the five-phase PMSM in the case of inter-tum short circuit fault helping to predict performances andor to extract fault signature in the machine main quantities. Simulation work has been carried out using MATLAB to verify the performance of the proposed detection/diagnosis method.

Fault Tolerant Control of Induction Motor Drives Subject to Rotor Resistance Adaptation

This paper describes the synthesis of a vector fault tolerant control of induction motor drives using an adaptive observer. This observer is used to detect the rotor resistance and flux components using the stator terminal voltages and currents. The rotor resistance is adapted using a new algorithm which does not imply a high computational load. Stability analysis based on Lyapunov theory is performed in order to guarantee the closed loop stability. The rotor resistance is used for the correction of the controllers and the rotor time constant. To verify the tolerance and the applicability of this control, we consider the stator inter-turn fault which is frequently encountered in practice. An analytical method for the modelling of this fault is presented. The equations which describe the transient as well as steady state behavior of unsymmetrical induction machine including the computation of machine inductances are presented. These inductances are calculated analytically using the magnetic field distribution through the machine air-gap. Simulation results are provided to evaluate the consistency and performance of the proposed fault tolerant control of induction motor based vector control.

Advanced model of IM including rotor slot harmonics

Purpose – The purpose of this paper is to present a detailed advanced dynamical model of induction machine (IM) with unskewed rotor bars, including rotor slot harmonics. Design/methodology/approach – Procedure of IM modeling using results from finite element analysis (FEA). Series of magneto-static FEA simulations are used to obtain matrix of IM inductances as a function of rotor angular position and geometry. Each element in this matrix is represented by Fourier series (FS) and incorporated in proposed dynamical model. Using or neglecting various elements in FS of inductance matrix may be useful for determining which component of the series has dominant influence on harmonic content of stator currents, torque ripple or speed variation. The usefulness of application of presented model is verified comparing with time-stepping FEA simulations. Findings – Although the model is not suitable for usage in on-line regulation of IM drives, but the results of simulations may be used to thoroughly explain origins of higher order harmonics in stator currents of IM and help improve sensorless speed estimation algorithms and fault diagnostics. Originality/value – This paper shows an approach to the modeling of IM which includes effects of non-uniform air gap and non-sinusoidal distributions of magneto-motive forces. Inductance matrix elements are complex functions of rotor position, geometry and winding distributions and it gives an opportunity for detail analysis of IM behavior in numerous applications.

Detection and Localization of Stator Resistance Dissymmetry Based on Multiple Reference Frame Controllers in Multiphase Induction Motor Drives

Multiphase drives are receiving increasing attention by the research community in high-power applications. In this paper, the behavior of multiphase induction machines with an odd number of phases is investigated under the assumption that the resistances of the stator winding are unbalanced owing to poor connections. A high-resistance connection can cause overheating and supply voltage unbalance, which may reduce the efficiency and increase the fire hazard. The main contribution of this paper is a control scheme that can detect the stator resistance unbalance, that can localize the faulty phase, and, at the same time, that can keep the drive behavior unchanged, both in transient and steady-state operating conditions. The control scheme is based on an analytical model that shows the effect of the unbalance on the current components related to the high-order spatial harmonics of the air-gap magnetic field. The theoretical analysis and the feasibility of the control scheme are confirmed by experimental tests.

Numerical investigation of the 3D vibrational behaviour of skewed induction machines due to rotating force waves

PurposeThe purpose of this paper is to analyse the surface vibrations of an induction machine due to force waves acting on the stator and rotor core. The focus lies on the investigation of the influence of force waves with axial variation and with higher spatial ordinal numbers on the surface vibration of an induction machine and thus its emitted noise.Design/methodology/approachUnit force waves with different spatial ordinal numbers and varying in axial direction are set up and applied on the stator and rotor teeth of a structural finite element model of an induction machine. Structural harmonic analyses with different frequencies are performed and the deformation of the machine is determined. After that, the root mean square of the normal component of the velocity on the surface of the machine's housing is determined and compared for the different force waves.FindingsThe influence of force waves with spatial ordinal numbers of higher order can have a significant influence on the structural vibration, especially if the spatial ordinal number is near the number of teeth. Furthermore, it is shown that the structure may react sensitively to axial variations of the forces, particularly near distinct structural resonances.Originality/valueThe presented investigations show relevant issues influencing the noise behaviour of electrical machines.

Shaft Positioning for Six-Phase Induction Machines With Open Phases Using Variable Structure Control

In this paper, a new variable structure control law is proposed in order to obtain the shaft positioning of a symmetrical six-phase induction machine when phases are lost and when large variations of inertia occur. The algorithm based on a time-varying switching line guarantees the existence of a sliding mode since the beginning of the shaft motion. Indeed, the surface is first designed to pass through the initial representative point and, subsequently, to move toward a predetermined desired surface via shifting. With this algorithm, the induction machine behavior is exactly the same in healthy or in faulted modes when one or more stator phases are lost and whatever the mechanical shaft configuration is. The capacities of this control technique with a mechanical sensor have been tested in simulation and then validated experimentally on a specific setup.

Validation of a Comprehensive Analytic Noise Computation Method for Induction Machines

The validation of an analytical approach to determine the noise behavior of induction machines is presented. Analytical electromagnetic, structural, and acoustical computations are performed. Data obtained by numerical computations as well as by vibration and noise measurements are compared with the analytical results.

Modular Approach for Investigation of the Dynamic Behavior of Three-Phase Induction Machine at Load Variation

In This paper, a modular approach for investigation of the dynamic behavior of three phase induction motor is developed and described in details. This model has been built up, systematically, by means of basic function blocks found with MATLAB/SIMULINK. This model is described in similar but modular approach as in electrical machines theory. The motor model includes multi-level blocks solving equations for each motor part or component. This approach enables the researcher to calculate or investigate any motor variables; voltage, current, flux, speed and torque. This model could also be used for a wide range of horse power needed in scientific research and numerical applications. A q-d axis based model is proposed to analyze the transient performance of three-phase squirrel cage induction motor using stationary reference frame. Constructional details of various sub-models for the induction motor are given and their implementation in SIMULINK is outlined. Direct-online starting under different load conditions of a 3 hp induction motor (as case study) is also studied. The motor stator voltage, the stator and rotor currents, the developed torque and rotor speed are, numerically, calculated and plotted for different operating conditions.

A coupled‐circuit model for a DFIG operating under unbalanced conditions

PurposeThe purpose of this paper is to describe the principles of a coupled‐circuit model for a doubly‐fed induction generator (DFIG) and to present evidence of the validity of this versatile and powerful technique and the advantages it offers when used for modeling and analysis of DFIG operation in unbalanced conditions. This paper also investigates the winding fault induced changes in the machine stator steady‐state current spectrum with a view to DFIG condition monitoring.Design/methodology/approachThe presented model is based on the summation of harmonic winding inductances. It comprises of a set of standard induction machine electromechanical equations where a connection matrix that defines a particular balanced/unbalanced winding configuration of interest is conveniently incorporated in the expressions. This model is therefore capable of representing both open‐ and short‐circuit stator and rotor winding faults while also taking into account higher order air‐gap field harmonics. Model predictions are verified in this work through comparison with corresponding experimental data obtained from a purpose built 30 kW DFIG laboratory test rig. The paper involves a number of healthy and faulty operating scenarios.FindingsAdvantages and validity of the employed model are illustrated in time and frequency domain for different steady‐state balanced/unbalanced winding DFIG operating conditions. It is also shown in both predicted and measured data that the considered winding asymmetries give rise to additional harmonic components in the stator current spectrum.Research limitations/implicationsThe importance of considering higher order air‐gap field harmonics when modeling induction machine behavior is outlined in this work.Practical implicationsThis paper identifies changes in the DFIG stator current harmonic content spectra that are winding fault induced. These may have the potential to constitute reliable fault indicators.Originality/valueThe paper discusses a harmonic conductor distribution‐based modeling method aimed predominantly at frequency domain analysis of DFIG electrical quantities. It is shown that DFIG stator current spectrum is rich in higher order harmonic components and that manner in which these are manifested is heavily influenced by the presence of winding unbalance.

A Transfer-Function-Based Thermal Model Reduction Study for Induction Machine Thermal Overload Protective Relays

High-order induction machine thermal models have been widely studied for the analysis of the thermal behavior of induction machines. However, the real-time implementation of such models for the online thermal protection of induction machines is very difficult due to the lack of accurate information on the machines. This paper proposes a novel simplified thermal model of induction machines for thermal overload relays. Instead of using a lumped thermal network, a transfer-function-based approach is proposed for reducing the order of induction machine thermal models. The proposed thermal model requires significantly fewer thermal parameters for the accurate modeling of the thermal behavior of the machine. The proposed thermal model is validated via experimental results on a 7.5-hp open-drip-proof induction machine under various load conditions. The major features of the proposed thermal model are the following: 1) high accuracy of the stator winding temperature estimation, with a root-mean-square error within 3°C; 2) low computational requirement, which reduces the cost of thermal overload relays; and 3) easy implementation since only current sensors are required.

Prediction of Audible Magnetic Noise Radiated by Adjustable-Speed Drive Induction Machines

This paper presents a fully analytical model of the electromagnetic and vibro-acoustic behavior of variable-speed squirrel-cage induction machines. This model is integrated in a fast simulation tool that can be used to design motors with low magnetic noise levels on their whole speed range. Some simulation results at variable speed are favorably compared with experiments at both vibratory (spectrograms) and acoustic levels (sonagrams) on several motors, on a wide power range (from 700 W to 250 kW). These extensive tests show that the model correctly predicts the main exciting forces, motor natural frequencies, and resonances during adjustable-speed drive. The simulation tool, called Diva, has been successfully applied to design a new low-noise ALSTOM motor.

From the ideal to the real induction machine: Modelling approach and experimental validation

The aim of this paper is to discuss the ability of a numerical code in reproducing a real machine behavior, with particular reference to the cage currents of a four-poles 50 Hz induction motor. The used 2D Finite Element method (FEM) is based on voltage driven field formulation, handling the nonlinearity by the fixed point technique and the rotor movement by the sliding mesh approach. The numerical outcomes are validated by experiments performed on a dedicated laboratory setup, able to provide the instantaneous cage currents. Then, a spectral algorithm has been applied to the experimental and computed variables and the results have been interpreted in terms of magneto-motive forces. This approach allows us to determine possible machine eccentricities or other asymmetries not introduced in the simulations. Discussing the computed and measured spectra and excluding in the last ones the lines corresponding to non-idealities, an evaluation on how the modelling approach reproduces accurately the real machine is possible. The validated model will be able to reproduce the machine behavior of usual induction machines whose rotor currents are not measurable.

Flicker Attenuation—Part II: Transfer Coefficients for Regular Voltage Fluctuations in Radial Power Systems With Induction Motor Loads

Electromagnetic compatibility standards and guidelines used for planning of flicker allocation at various busbars of a power system requires some knowledge of the manner in which voltage fluctuations and hence the flicker propagate and how various loads respond to them. The current rudimentary approach taken for the determination of the load response to voltage fluctuations is based on network impedance values and hypothetical dynamic impedance values of the connected loads. Practical results and recently developed theory on the subsynchronous behavior of induction machines suggest that where there is a large base of induction machine exists on a power system the flicker attenuation is significant. This paper reports on a methodology to include the influence of induction machine behavior in flicker propagation and attenuation studies. The work is based on small-signal models to describe induction machine and system behavior which are utilized for the development of a flicker transfer coefficient. A systematic approach for the practical application of the methodology for flicker related work is included.

MATLAB simulation of induction machine with saturable leakage and magnetizing inductances

At high stator phase currents, the effect of saturation of the stator and rotor leakage inductances becomes noticeable to the extent that the conventional machine model fails to represent the dynamic performances of induction machine. In this paper, a commercial software package, MATLAB is used to simulate the dynamic behaviour of induction machine with saturable inductances. The computer results presented in this paper show the errors resulting when the magnetizing, stator and rotor leakage inductances are assumed constant as in the case of conventional machine model. Key Words: Simulation, Saturation effect, Induction machine, Transient state, MATLAB. Botswana Journal of Technology Vol.13(2) 2004: 20-28

Generator operations of saturated induction machines

This paper shows that, due to the saturation of the main magnetic circuits, the generator behaviour of induction machines may not be evaluated theoretically with accuracy by means of traditional mathematical models, especially when operations at variable frequencies are dealt with. For this reason the paper presents a mathematical model of saturated machines. Voltage and current space vectors are used. The model has been carried out on the basis of two air-gap machine inductances (one differential and the other rational) previously introduced by another author (Kovacs, 1984). It has been validated at steady state by comparing the theoretically evaluated and experimentally measured armature currents of a mass-produced machine. The influence of saturation on armature current amplitudes is evidenced by comparing numerical results obtained by the suggested model with those of a traditional model. The model is also used for the performance analysis of dynamic and steady-state generator behaviour of cylindrical induction machines and for carrying out conditions that obtain self-excitation and stable operations of machines supplying passive electrical networks.

Closed-loop control impact on the diagnosis of induction motors faults

In this paper, the impact of control on faulted induction machine behavior is presented. The diagnostic indexes usually used for open-loop operation are no more effective. Simulation and experimental results show that the spectrum of the field current component i/sub d/ in a field-oriented controlled machine has suitable features that can lead to an effective diagnostic procedure for closed loop induction machines. Specifically in case of stator and rotor faults, the spectrum components at frequencies respectively -f and 2sf are quite independent of control parameters and dependent on the fault extent.