Horia Gavrila

The influence of punching and laser cutting technologies on the magnetic properties of non-oriented silicon iron steels

Punching and laser cutting of non-oriented silicon iron sheets (NO FeSi) determine changes in the material at the cutting edge, which produce an important effect on the magnetic properties. Through punching it results a plastic deformation in the zone near the cutting edge. Laser cutting technology causes thermal stresses, which alter also the magnetic properties. The knowledge of the type of deterioration is very important for the production of the electrical machines, because of the increased total losses. There were tested steel samples of NO FeSi grades, M400-65A and M800-65A, with an area of 300 × 30 mm2. The magnetic properties were measured with a laboratory single strip tester in the range of frequency from 10 ÷ 400 Hz at 1 T peak magnetic polarization.

In Situ Evaluation of Ferromagnetic Bodies Magnetic Characteristics

The B-H characteristic of an iron body material influences the magnetic field measured in the air. On principle, one can pose the problem of B-H relation determination, by making measurements of the magnetic induction in the neighbourhood of the body. Unfortunately, we have an ill-posed inverse magnetic field problem, for which there is possible that, big variations of the BH characteristic to produce only very small modifications of the magnetic field in the air. It is essential to use a sufficiently sensitive computation procedure in order to produce credible results. This paper proposes a device for the B-H characteristic evaluation, admitting that inside the ferromagnetic bodies the magnetic field distribution is not uniform.

Experimental analysis of magnetic anisotropy in silicon iron steels using the single strip tester

The standard magnetic measurements, for grain oriented (GO) and non-oriented (NO) electrical steels (FeSi), are made using the Epstein frame or the single strip tester. The magnetic characterization is limited to the rolling direction cut samples for the FeSi GO materials. For the NO ones, the standard measurements give an average of the magnetic behavior in the rolling and the transverse directions. In this article is analyzed the magnetic anisotropy of FeSi NO and FeSi GO strips, with the surface area of 300 × 30 mm2. The measurements were performed with an unidirectional single strip tester on FeSi strips cut at 0°, 15°, 30°, 45°, 60°, 75°, 90° with the rolling direction. It was determined the hard and the easy axis of the samples and the influence of the anisotropy on the energy losses and relative magnetic permeability. The loss behavior of these alloys was studied as a function of frequency in the range of 5 Hz to 200 Hz at a given magnetic polarization (Jp) of 1 T.

Some important effects of the water jet and laser cutting methods on the magnetic properties of the non-oriented silicon iron sheets

Nowadays it is very important to use non-oriented electrical alloys, which must have a very good quality and must be cut through a proper method that leads to a minimum energy loss value. The manufacturers of the electrical machines want to minimize the damage of the magnetic properties during the cutting process, in order to produce high efficiency motors or generators. In this paper are presented two non-conventional cutting technologies, which are used in the prototype production of the magnetic cores. These two methods have significant effects on the area near the cut edge; the water jet produces important burs and oxidation of the material and the laser cutting generates high local thermal stresses that increase the total energy losses of the magnetic core. There were tested steel samples of fully processed non-oriented alloys (NO FeSi) grades, M400-65A and M800-65A, with an area of 300 × 30 mm2. The magnetic properties were measured with a laboratory single strip tester in the range of frequency from 10 ÷ 400 Hz at 1 T peak magnetic polarization.

Magnetic Materials Used in the Magnetic Core Manufacture of Electrical Machines and Transformers

Two types of silicon iron steels, M400-65A non-oriented and MOH grain-oriented alloys were characterized using an industrial Brockhaus Single Strip Tester at two peak magnetic polarizations of 500 mT and 1000 mT in the frequency range from 10 Hz to 100 Hz. The samples were cut parallel to the rolling direction trough different cutting technologies, which are the classical mechanical-, then the non-conventional laser-, water-jet-and traveling wire electro-erosion methods. The loss separation concept was applied and the total energy losses, determined experimentally, for each sample were decomposed into hysteresis, classical (Foucault) and excess (anomalous) energy losses. A detailed analysis of each type of losses as a function of the frequency was made and the influence of the cutting technology was analyzed.

Influence of increase mechanical cutting degradation on 50 Hz magnetic properties of non-oriented electrical steels

In this paper is point out the influence of the classical mechanical cutting on the magnetic properties of three industrial non-oriented electrical steels M400-50A, M400-65A and, M700-50A. The selected materials were magnetically characterized and analyzed at 50 Hz and at a peak magnetic polarization JP ∈ {50, 100, 250, 500, 800, 1000, 1100, 1200, 1300, 1400, 1500} mT. Based on the complex permeability concept, in which the total permeability is divided into two parts, the real and the imaginary component, the measured values are presented. All the investigated strips have a length of 300 mm and, to magnify the degradation, a decreasing width of 30, 15, 10, 7.5 and 5 mm were chosen. The magnetic characterization was performed on a laboratory single strip tester (SST) set-up, which can make standardized measurements on samples with an area of 300 mm × 30 mm. To reassemble the standard width of 30 mm, there were put together side by side 2, 3, 4 and 6 pieces.

Magnetic properties of nanocrystalline films and amorphous Co-rich alloys

The paper presents a comparative study of two magnetic materials: Co-rich nanocrystalline and amorphous films of the same compositions, obtained by electroplating at different current density. The electrodeposited Co-rich alloys formed at 20-30 mA/cm2 are nanocrystalline and have the same magnetic behavior and a good stability.

Mechanical cutting influence on the energy losses in non oriented silicon iron steels

Mechanical cutting technology is a worldwide method, used to cut the magnetic cores of the electrical machines nowadays. The manufactures of the electrical devices prefer cutting the non oriented steel through this classical method, due to the fact that it is the cheapest of all. Non oriented silicon iron alloys (NO FeSi) are mainly characterized by specific energy losses. The mechanical properties and the coatings of the material become important, because they influence the power density and the cost of the resulting electric machine. There were tested strips of M800-65A industrial steel grade, cut through punching technology. All samples have the length equal to 300 mm and the width of 30, 15, 10, 7.5 and 5 mm. The magnetic characterization was performed using a laboratory single strip tester, which can make measurements on samples with an area of 300 × 30 mm2. To have the standard width of 30 mm, there were put together side by side 2, 3, 4 and 6 pieces with different widths. The magnetic properties were analyzed at 1000 mT and 1500 mT in the frequency range 10 ÷ 200 Hz.

Prediction of the Energy Losses in Soft Magnetic Alloys Based on the Magnetic Objects Theory in the Case of the Uniform Magnetic Flux Penetration

We report an investigation and a theoretical assessment of energy loss prediction in crystalline and amorphous soft magnetic materials. There were tested a sample made from non-oriented silicon iron (NO FeSi) M800-65A, industrial type alloy, cut longitudinally to the rolling direction and a toroidal sample of Co67Fe4B14.5Si14.5 amorphous ribbon. The losses behaviour of the crystalline NO FeSi strip was studied as function of frequency in the range of 5 Hz to 200 Hz at a given magnetic polarization (Jp) of 0.5 T and 1 T. In the case of the amorphous Co-based ribbon the losses variation was studied as function of frequency in the range of 5 Hz to 10 kHz at a given magnetic polarization of 20 mT. Using the concept of loss separation for the data analysis, in the approximation of linear magnetization law and low frequency limit, it can be considered in both cases, that the excess losses can be quantitatively assessed within the theoretical framework of the statistical loss model based on magnetic object theory.