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Kozlowski A.,MAGNETO Ltd. | Rygal R.,MAGNETO Ltd. | Zurek S.,Megger Instruments Ltd.
IEEE Transactions on Magnetics | Year: 2014

A large dc electromagnet with a 200 mm long air gap was designed, constructed, and tested. Analytical calculations provided the first approximation of required parameters. The design was refined with the aid of finite element modeling. Thermomagnetic processing required nominal flux density level to be 0.35 T. It was validated on a prototype that the average flux density in the air gap exceeded this value. The magnetizing coils were designed to be cooled by natural air convection. Despite a large size (∼1900 kg), the electromagnet was designed to consume less than 2.5 kW and could be energized from a single-phase mains socket. © 2014 IEEE.

Zirka S.E.,Dnipropetrovsk National University | Moroz Y.I.,Dnipropetrovsk National University | Steentjes S.,RWTH Aachen | Hameyer K.,RWTH Aachen | And 3 more authors.
Journal of Magnetism and Magnetic Materials | Year: 2015

We consider dynamic models, both numerical and analytical, that reproduce the magnetization field H(B) and the energy loss in ferromagnetic sheet materials with different domain structures. Conventional non-oriented (NO) and grain-oriented (GO) electrical steels are chosen as typical representatives of fine-domain and coarse-domain materials. The commonly-accepted loss separation procedures in these materials are critically analyzed. The use of a well-known simplified ("classical") expression for the eddy-current loss is identified as the primary source of mistaken evaluations of excess loss in NO steel, in which the loss components can only be evaluated using the Maxwell (penetration) equation. The situation is quite different in GO steel, in which the loss separation is uncertain, but the total dynamic loss is several times higher than that explained by any version (numerical or analytical) of the classical approach. To illustrate the uncertainty of the loss separation in GO steel, we show that the magnetization field, and thus the total loss, in this material can be represented with equal accuracy using either the existing three-component approach or our proposed two-component technique, which makes no distinction between classical eddy-current and excess fields and losses. © 2015 Elsevier B.V. All rights reserved.

Zurek S.,Megger Instruments Ltd.
International Journal of Applied Electromagnetics and Mechanics | Year: 2015

Measurements of magnetic properties of toroidal samples of magnetically soft materials are defined by the group of international standards IEC 60404. These standards do not specify the actual value of the shunt resistor, but for instance just the fact that it should be "non-inductive". This study provides more information on the topic of selection of shunt resistance, which is crucial for many studies of magnetic measurements. It was found that the resistance value of a shunt resistor has no direct effect on the measurement results of magnetic properties. The quality of calibration of the value does have a direct effect, but not the value itself and it could have any value from 0.1 Ω to 10.0 Ω (as investigated). Care must be taken so that additional device-specific effects are not induced in the measurement equipment (e.g. reduced accuracy at the lowest or highest input ranges). The value of the shunt resistor should be such that the voltage drop across it would coincide with the most accurate input range of the voltmeter or data acquisition device. © IOS Press and the authors. All rights reserved.

Soinski M.,Czestochowa University of Technology | Pluta W.,Czestochowa University of Technology | Zurek S.,Megger Instruments Ltd. | Owski A.K.,MAGNETO Ltd.
International Journal of Applied Electromagnetics and Mechanics | Year: 2014

Instrument current and voltage transformers remain the basic apparatus used in measurements of energy in electrical grid. Increasing importance of distributed energy sources necessitates more precise measurements of consumed as well as generated electrical energy. Both types occur in low voltage network where the main focus is on current transformers for electronic-type electrical energy meters. These current transformers should fulfil many requirements for precise electrical energy measurements. This paper presents a modern system for measurement of various metrological features of current transformers. © 2014 - IOS Press and the authors.

Zurek S.,Megger Instruments Ltd.
IEEE Transactions on Magnetics | Year: 2012

The paper describes results of two-dimensional finite element modeling of cut (gapped) magnetic cores. The influence of an irregular air gap on the apparent permeability of the core is calculated. Two magnetically soft materials are used: electrical steel M-27 and supermalloy (80% Ni). The results indicate that decreasing the minimum air gap between parts of the core can increase the initial effective permeability of the core, by a factor of 2 or 3 × despite the total volume of the gap remaining unchanged. © 2006 IEEE.

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