Iron Losses Prediction with PWM Supply Using Low and High Frequency Measurements: Analysis and Results Comparison

In this paper, two different methods for iron loss prediction are analyzed. The first method is based on the classical separation of loss contributions (hysteresis, eddy-current, and excess losses). The model requires loss contribution separation using iron loss measurements with sinusoidal supply. In this paper, this method will be called the ldquolow-frequency method.rdquo The second method, named the ldquohigh-frequency method,rdquo is based on the assumption that, under pulsewidth modulation supply, the higher order flux density harmonics do not influence the magnetic work conditions. These magnetic conditions depend only on the amplitude of the fundamental harmonic of the flux density. In this paper, both the proposed methodologies and the related measurements are described in detail, and the obtained results are compared with the experimental ones. The experimental results show that both methods allow getting excellent results. The high-frequency method is better than the lower one but requires a more complex test bench. Depending on the accuracy required by the user, the more handy method can be chosen, with the guarantee that the estimation errors will be lower than 5

Opportunities and Precautions in Measurement of Power Loss in Electrical Steel Laminations Using the Initial Rate of Rise of Temperature Method

A system has been developed for measuring localized power loss of electrical steel laminations based on the initial rate of rise of temperature method. Hardware and software components were designed and developed individually to make an accurate measuring system. Three experiments were carried out to calibrate the system and quantify its accuracy over a wide measurement range. The application of the measuring system was demonstrated in two cases of measuring localized power losses near bolt holes in laminations and near artificial lamination edge burrs in a 300 kVA, 3 phase transformer core. The experimental results show that the developed system can measure localized power loss over a wide range with uncertainty of measurement less than ± 2%, but precautions are necessary when interpreting measurements in regions where the magnitude of the loss varies significantly over distances of less than a few centimeters

Influence of cutting process on magnetic properties of electrical steel

La tesi fornisce un'analisi quantitativa del degrado delle proprietà magnetiche a seguito di tranciatura e taglio al laser su lamierini in acciaio magnetico M270-50A. Le misure sui campioni sono state ottenute con un'Apparecchio di Epstein grazie al quale sono state misurate la riduzione della permeabilità magnetica e l'aumento delle perdite specifiche nei campioni. Le misure sono state utilizzate per valutare gli effetti su una macchina asincrona tramite simulazione agli elementi finit

Application of improved core loss formulations to machine design

Includes abstract.Includes bibliographical references (p. 117-120).The primary focus of this thesis is in core loss measurement and modeling techniques and their impact in machine design. In practice, steel manufacturers usually supply core loss data either at 50/60Hz, 1.5T or curves (core loss vs. flux density) at 50 and/or 60Hz. There is growing need for lamination characterization at high flux densities (2T) and high frequencies (3.2 kHz) for novel electric machine designs operating at high speeds. The core loss measurement concept is reviewed first. Two core loss measurement formulae are compared using core loss results from different testing frames and materials

Modeling of Core Losses in Electrical Machine Laminations Exposed to High Frequency and Non-sinusoidal Flux

Electrical machines account for about 60% of the electricity consumption in industrial countries; hence a huge energy savings could be achieved by even a small increment in the machine efficiency. Improving the designs of electrical machines requires accurate quantification of the machine losses. A significant portion of the losses in electrical machines is caused by the core loss in the magnetic material. The physical mechanism of core losses is still an open problem, and most of the available core loss models are based on limited curve fitting techniques, instead of a physical understanding of magnetic material behaviour. In this thesis, a new method is proposed to separate the core loss components in laminations exposed to high frequency excitations. Accurate separation of core losses is achieved by calculating the hysteresis energy loss at each frequency, taking into account the flux density distribution. The results highlight that the conventional assumption of constant hysteresis energy loss per cycle is only valid at low frequencies, where skin effect is negligible. In addition to the new separation method, a physics based core loss model is developed to estimate core losses in electrical machine laminations exposed to non-sinusoidal flux. The developed model accounts for the effects of the non-uniform flux density inside the lamination. The model results are verified experimentally by comparing with the measured core losses in laminations exposed to the flux waveforms in different sections of permanent magnet (PM) and switched reluctance (SR) machines

Experimental and Theoretical Analysis of Soft Magnetic Materials for Power applications

The efficiency of electrical machines carries a global impact because they fulfill about three-quarters of global electrical energy consumption. Its improvement requires a sound knowledge of energy loss properties of magnetic materials used in the core of electrical machines, especially non-conventional supply conditions, such as non-sinusoidal, high induction, alternating (1-D) and rotating (2-D) flux waveforms that have been posed with the incorporation of new electronic devices and materials in the systems. For these reasons, novel theoretical models and experimental techniques need to be developed to obtain the loss behavior under these complex flux regimes. To address these issues, experimental investigation and theoretical analysis have been carried out in this thesis on different magnetic materials and a wide ensemble of supply conditions. The aim of the theoretical analysis was to fill the gap between the physicists and the engineers by developing simple models that can be applied to compute the loss under realistic supply conditions. This theoretical frame is rooted in the physical principle of the separation of loss and the Statistical Theory of Loss (STL) by which the loss can be separated into the hysteresis, classical, and excess components. The concept of loss separation has been exploited under 1-D flux and extended to 2-D fluxes, where the relations between alternating and rotational losses have been obtained on a number of different materials, this analysis restricted to the region not influenced by skin effect. The proposed theoretical models have been tested by comparing loss figure of different magnetic materials over a wide range of frequencies, induction levels, and conventional or non-conventional supply conditions. To this purpose, loss characterization of non-oriented Fe-(3.2wt \%)Si steels have been performed using a three phase magnetizer able to generate 1-D and 2-D flux patterns, up to saturation magnetization. Fieldmetric and Thermometric methods have been applied at low and very high induction levels. Loss characterization of other non-oriented Fe-Si and low carbon steels have also been performed under 1-D flux at very low and high sinusoidal inductions using Epstein frame, single sheet tester or ring samples, over frequencies ranging from quasi-static conditions up to 10 kHz. Systematic uncertainties have been observed in measurements using a Single Sheet Tester due to MMF drop in flux closing yoke and a compensated Permeameter has been designed to reduce these uncertainties by compensating the MMF drop in the flux closing yoke

Equation-of-State Dependent Features in Shock-Oscillation Modulated Neutrino and Gravitational-Wave Signals from Supernovae

We present 2D hydrodynamic simulations of the long-time accretion phase of a 15 solar mass star after core bounce and before the launch of a supernova explosion. Our simulations are performed with the Prometheus-Vertex code, employing multi-flavor, energy-dependent neutrino transport and an effective relativistic gravitational potential. Testing the influence of a stiff and a soft equation of state for hot neutron star matter, we find that the non-radial mass motions in the supernova core due to the standing accretion shock instability (SASI) and convection impose a time variability on the neutrino and gravitational-wave signals. These variations have larger amplitudes as well as higher frequencies in the case of a more compact nascent neutron star. After the prompt shock-breakout burst of electron neutrinos, a more compact accreting remnant radiates neutrinos with higher luminosities and larger mean energies. The observable neutrino emission in the direction of SASI shock oscillations exhibits a modulation of several 10% in the luminosities and ~1 MeV in the mean energies with most power at typical SASI frequencies of 20-100 Hz. At times later than 50-100 ms after bounce the gravitational-wave amplitude is dominated by the growing low-frequency (<200 Hz) signal associated with anisotropic neutrino emission. A high-frequency wave signal is caused by nonradial gas flows in the outer neutron star layers, which are stirred by anisotropic accretion from the SASI and convective regions. The gravitational-wave power then peaks at about 300-800 Hz with distinctively higher spectral frequencies originating from the more compact and more rapidly contracting neutron star. The detectability of the SASI effects in the neutrino and gravitational-wave signals is briefly discussed. (abridged)Comment: 21 pages, 11 figures, 45 eps files; revised version including discussion of signal detectability; accepted by Astronomy & Astrophysics; high-resolution images can be obtained upon reques