IEC 61631:2020 pdf download

IEC 61631:2020 pdf download.Test method for the mechanical strength of cores made of magnetic oxides
1 Scope
This document specifies a test method for the mechanical strength of cores made of magnetic oxides. This test method is suitable for most of the E-cores, ETD-cores, I-cores and ring- cores but other core types such as U-cores could be tested according to a derived method agreed by the parties concerned. This document is also applicable to the mechanical strength measurement of magnetic powder cores.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 7500-2, Metallic materials – Verification of static uniaxial testing machines – Part 2: Tension creep testing machines – Verification of the applied force
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses:  IEC Electropedia: available at http://www.electropedia.org/ ISO Online browsing platform: available at http://www.iso.org/obp 3.1 mechanical strength maximum recorded force at the instant of fracture of a magnetic oxide core when it is loaded with the bending stress
4 Apparatus
4.1 Test core support and loading wedge Test cores shall be supported on free moving roller bars or on a flat support depending on their size (see 6.2). The loading wedge, the roller bars and the stretch bar or the flat support shall be made of hardened steel with a hardness of 40 HRC (HRC is Rockwell hardness) to 60 HRC. The loading wedge and the roller bars shall have a radius of 2 mm. The radius of the contact part of the stretching rod head and the measured core is 2 mm. The loading wedge and the stretch bar shall be connected to a device for measuring and recording the load applied.4.2 Testing device The testing device shall be a mechanical testing machine capable of applying a force to the loading wedge high enough to break the test core. The machine shall be capable of applying the force at a constant loading rate. The machine shall be equipped with a device for recording the peak load applied to the test core. The accuracy of the machine shall be 1 % of the indicated load. The force calibration of the machine shall be checked in accordance with ISO 7500-2. 4.3 Humidity measuring device A humidity measuring device, such as, but not limited to, an aspirated psychrometer or whirling psychrometer that is capable of measuring relative humidity to an accuracy of ±2 % shall be used.
5 Test cores
5.1 General The test cores shall be selected as agreed between the parties concerned. They may be machined to the specified dimensions, because any machined surface plays an important role in the mechanical strength (see the Introduction). 5.2 Number of test cores For material development, characterization or quality checking, the minimum number of test cores shall be five pieces. For statistical evaluation of strength data (for example, Weibull parameters), the minimum number shall be thirty. For comparison of data for different materials, it is important that the number of specimens is high enough to obtain results with sufficient statistical confidence. Since the confidence limits, in general, depend on the number of test results and their dispersion, the number of test specimens should be decided on the basis of statistical considerations. 5.3 Precautions The prepared test cores should be handled with care to avoid introduction of additional damage. Test cores should be kept separately at all times, and should be wrapped individually for transport.