Ahmed Mohamed Abouelyazied Abdallh

An Inverse Approach for Magnetic Material Characterization of an EI Core Electromagnetic Inductor

In this paper, the complete magnetic material characteristic, hysteretic and anhysteretic, is reconstructed for an EI electromagnetic inductor. The material identification process, including air gap assessment, is carried out using a coupled experimental-numerical inverse technique, based on a set of well chosen global and local magnetic measurements. It is shown that a higher accuracy is obtained when local measurements are performed in regions with less stray fields, and the air gap assessment is strongly improved by the use of local magnetic measurements.

Magnetic Material Identification in Geometries With Non-Uniform Electromagnetic Fields Using Global and Local Magnetic Measurements

In this paper, the magnetic material characteristics are reconstructed for magnetic circuits with non-uniform electromagnetic field patterns, including excitation winding and/or air gaps, as in the case of rotating electrical machines. The identification process is done using a set of well chosen global and/or local magnetic measurements. Moreover, numerical inverse techniques are implemented in order to reconstruct the material characteristics from a limited number of global and/or local measurements.

Identification of Demagnetization Faults in Axial Flux Permanent Magnet Synchronous Machines Using an Inverse Problem Coupled With an Analytical Model

This paper presents an analytical method for permanent magnet demagnetization detection in an axial flux permanent magnet synchronous machine. First, a forward model is built to calculate the three phase terminal voltages with inputs of three phase currents, the geometry of the machine, and the electromagnetic properties of the machine. To model the demagnetization fault, the scalar potential equation is solved. The magnetization waveform is a square wave corrected with magnetization factors that represent the individual magnetization of every magnet. Second, the forward model is inverted so that the magnetization factors are computed out of the three phase currents and the three phase terminal voltages. The forward model is validated with experimental data and finite element simulations.

A Non-Destructive Methodology for Estimating the Magnetic Material Properties of an Asynchronous Motor

In this paper, the magnetic material characteristics, the normal magnetizing B - H curve and the loss parameters, are reconstructed for an asynchronous motor. The identification process is carried out using a coupled experimental-numerical inverse technique. Different inverse problems are formulated based on global and local magnetic measurements at no load condition. It is shown that a higher accuracy of identifying the normal magnetizing curve is obtained when local magnetic measurements are performed. In addition, loss parameters are recovered with an acceptable recovery error. The presented results are validated by comparison with the exact material characteristics. The presented results depict that the magnetic characteristics of the material inside a commercial asynchronous motor can be identified accurately by interpreting local magnetic measurements into a numerical model.

Local magnetic measurements in magnetic circuits with highly non-uniform electromagnetic fields

In this paper, local magnetic measurements are carried out in magnetic circuits with non-uniform electromagnetic field patterns, including excitation windings and/or air gaps, as in the case of rotating electrical machines. The effects of sensor choice, sensor noise sensitivity and electromagnetic field inhomogeneity on the accuracy of the identification of the magnetic material properties are investigated. Moreover, the validity of the local magnetic measurements is confirmed by numerical models, based on the finite element method. The paper comprehensively discusses the possibilities, difficulties and limitations of local magnetic measurements in magnetic circuits with non-uniform electromagnetic fields. It is shown that higher accuracy is obtained when the measurements are performed in regions with less stray fields.

Effect of Multilevel Inverter Supply on Core Losses in Magnetic Materials and Electrical Machines

The effect of multilevel inverter supply on power losses in magnetic cores and electrical machines is studied. A dynamic numerical model for the hysteresis, eddy current, and excess losses in a core lamination is first developed. By both measurements and simulations for a ring-core inductor, we demonstrate how increasing the number of inverter voltage levels decreases the iron losses when compared with traditional two-level supply. Although the switching frequency has a significant impact on the iron losses in the case of a traditional two-level inverter, using three or five voltage levels makes the losses almost independent of the switching. Finally, finite-element simulations show that similar reductions are also possible for the core losses of 150-kVA and 12.5-MW wound-field synchronous machines, in which rather low switching frequencies are typically used. Calorimetric loss measurements are also presented for the 150-kVA machine in order to confirm the significant effect of switching frequency on the core losses with two-level inverter supply.

Magnetic material identification of a switched reluctance motor

The identification of the magnetic material characteristics for the switched reluctance motor by solving an inverse problem is presented. The inverse problem aims at identifying the magnetic material parameter values of the magnetic circuit, starting from measured torque profiles. The computational time of the inverse problem is appreciably reduced by implementing a space mapping-based inverse approach. Using the space mapping technique, we combine the computationally intensive finite elementmodel with amuch faster magnetic network model. The proposed approach is very helpful for thematerial identification problem on the electrical machine, and the obtained results reveal the success and the reliability of the proposed scheme.

Optimal needle placement for the accurate magnetic material quantification based on uncertainty analysis in the inverse approach

The measured voltage signals picked up by the needle probe method can be interpreted by a numerical method so as to identify the magnetic material properties of the magnetic circuit of an electromagnetic device. However, when solving this electromagnetic inverse problem, the uncertainties in the numerical method give rise to recovery errors since the calculated needle signals in the forward problem are sensitive to these uncertainties. This paper proposes a stochastic Cramer–Rao bound method for determining the optimal sensor placement in the experimental setup. The numerical method is computationally time efficient where the geometrical parameters need to be provided. We apply the method for the non-destructive magnetic material characterization of an EI inductor where we ascertain the optimal experiment design. This design corresponds to the highest possible resolution that can be obtained when solving the inverse problem. Moreover, the presented results are validated by comparison with the exact material characteristics. The results show that the proposed methodology is independent of the values of the material parameter so that it can be applied before solving the inverse problem, i.e. as a priori estimation stage.

A Comparative Study of the Effect of Different Converter Topologies on the Iron Loss of Nonoriented Electrical Steel

In this paper, a comparative study of the effect of different converter topologies on the iron loss of nonoriented electrical steel is presented. Three converter topologies are considered in this investigation; namely: two-, three-, and five-level power converters. Moreover, the effect of the carrier frequency on both the iron loss and converter loss is introduced. The experimental results show a dramatic increase of the iron loss for the two-level converter, especially for low levels of the carrier frequency. Furthermore, the increase of the iron loss is negligible for the multilevel converter topologies. Specifically, the use of the five-level converter, even at a low value of the carrier frequency, results in lower iron losses than the three-level converter at a relatively higher carrier frequency.

Selection of Measurement Modality for Magnetic Material Characterization of an Electromagnetic Device Using Stochastic Uncertainty Analysis

Magnetic material properties of an electromagnetic device (EMD) can be estimated by solving an inverse problem where electromagnetic or mechanical measurements are adequately interpreted by a numerical forward model. Due to measurement noise and uncertainties in the forward model, errors are made in the reconstruction of the material properties. This paper describes the formulation and implementation of a time-efficient numerical error estimation procedure for predicting the optimal measurement modality that leads to minimal error resolution in magnetic material characterization. We extended the traditional Cramér-Rao bound technique for error estimation due to measurement noise only, with stochastic uncertain geometrical model parameters. Moreover, we applied the method onto the magnetic material characterization of a Switched Reluctance Motor starting from different measurement modalities: mechanical; local and global magnetic measurements. The numerical results show that the local magnetic measurement modality needs to be selected for this test case. Moreover, the proposed methodology is validated numerically by Monte Carlo simulations, and experimentally by solving multiple inverse problems starting from real measurements. The presented numerical procedure is able to determine a priori error estimation, without performing the very time consuming Monte Carlo simulations.