Standard method of magnetostriction measurement of grain-oriented electrical steel strip and sheet by means of a single sheet tester and an optical sensor was established as IEC 60404-17 Ed.1 [1] by the IEC/TC68 after intense considerations among magnetostriction experts. A new idea called "bridge" was introduced in order to minimize effects due to mechanical factors and other improvements were made. The 4th international round robin test (RRT) was carried out in 2020 and it was confirmed that the measurement reproducibility of the peak-to-peak value of magnetostriction improved from 5% or less in the 3rd RRT to 2% or less.

Standardization of the method of measurement of AC magnetostriction characteristics of grain-oriented electrical steel strip and sheet by means of a single sheet tester and an optical sensor, i.e. IEC 60404-17 Ed.1 [1], has been promoted in the IEC/TC68/WG2 to meet the demand of transformer industry. The relationship between the magnetostriction characteristics of grain-oriented electrical steel and transformer noise is complicated and yet not fully understood. One of basic problems has been the lack of a standard for the magnetostriction measurements. The measurement requires detection of slight vibration of the test specimen at a resolution of 0.01 mu m/m or better. In order to ensure this resolution, not only magnetic aspects but also mechanical aspects of the test apparatus, e.g. the influence of friction and external vibrations, have to be specified. The size of test specimen is restricted to 100 mm x 500 mm. The flux closer is a vertical single yoke or a horizontal double yoke. In order to avoid the influence of friction and vibration, no weight is put on the test specimen except an optical target and a clamp to fix the test specimen to the test apparatus. Also, no weight is connected to the end of test specimen to prevent additional vibration modes. The optical target is low mass and made of non-magnetic and non-conductive materials. The optical target and the clamp are placed between opposite pole faces of the yoke. In order to realize a low and constant friction coefficient, an insertion sheet with a thin fluorine resin-impregnated glass cloth adhesive film on its upper surface is placed under the test specimen. A round robin comparison using different test setups in accordance with the draft of standard was carried out.

Residual stress and high complexity of the dynamic magnetization conditions can significantly influence magnetic properties of materials used in automotive applications. The residual stress remaining in the motor laminations after manufacturing processes, such as punching and welding, has a detrimental effect on power loss and permeability of stator and rotor cores resulting in reduced efficiency and impaired performance. Moreover, the rotational and non-sinusoidal dynamic magnetization increase the loss in laminated stator stacks which can be significantly higher than under standard sinusoidal excitation. Therefore, Brockhaus Measurements developed a wide range of measurement technologies for comprehensive characterization of magnetic properties of electric motor materials. In this publication the examples of experimental data obtained with Brockhaus measurement systems for demonstrating impact of manufacturing and complex magnetization conditions on properties of stator cores and electrical steel laminations are presented and discussed.

In recent years, the field-metric method for measuring the joule losses set up in an electrical steel laminate when subjected to a rotating field has gained popularity. The ideal geometry of the magnetiser required to set up such a field is still however the subject of much debate. The work presented in this paper aims at providing some useful guidelines which might be considered when undertaking the construction of the simplest of such magnetizing setups having four salient poles excited by a two phase system and using a square sample. A 3D model for this rotational power loss tester was simulated for different pole geometries with the induction uniformity being assessed for every alteration.