Detail of GB/T 44391-2024

Introduction of GB/T 44391-2024

GB/T 44391-2024 Methods of measurement of the magnetostriction characteristics of grain-oriented electrical steel strip and sheet by means of a single sheet tester and an optical sensor 1 Scope This document defines the general principles and technical details of the measurement of magnetostriction characteristics of grain-oriented electrical steel strip and sheet by means of a single sheet tester and an optical sensor. It specifies the measurement procedure, calculation of the properties, reproducibility of the peak-to-peak value λp-p, the measurement setup and the test report. This document is applicable to grain-oriented electrical steel strip and sheet specified for the measurement of magnetostriction characteristics under an applied AC magnetic field at 50 Hz or 60 Hz. Note 1: The accelerometer method[9] is also an established method for the measurement of magnetostriction. However, it is more suited to the measurement of magnetostriction under an externally applied tensile or compressive stress, not zero stress, because it places a weight on the test specimen to prevent a deformation of the test specimen. Since this document includes the measurement at zero stress, the optical sensor method is provided as the optimum method. This document is applicable to the measurement of: ——the butterfly loop; ——the peak-to-peak value λp-p ; ——the zero-to-peak value λ0-p . The magnetostriction characteristics are determined for a sinusoidal induced secondary voltage, for a specified peak value of the magnetic polarization and at a specified magnetizing frequency. Note 2: Throughout this document the term “magnetic polarization” is used as described in IEC 60050-121. In some standards related to electrical steel, the term “magnetic flux density” is used. 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. GB/T 3785.1-2023 Electroacoustics - Sound level meters - Part 1: Specifications (IEC 61672-1:2013, IDT) IEC 60050-103 International Electrotechnical Vocabulary - Part 103: Mathematics - Functions Note: GB/T 2900.92-2015, Electrotechnical terminology - Mathematics - Functions (ISO 60050:2009, IDT) IEC 60050-121 International Electrotechnical Vocabulary - Part 121: Electromagnetism Note: GB/T 2900.60-2002, Electrotechnical terminology - Electromagnetism (eqv IEC 60050-121:1998) IEC 60050-221 International Electrotechnical Vocabulary - Chapter 221: Magnetic materials and components Note: GB/T 9637-2001, Electrotechnical terminology - Magnetic materials and components (IEC 60050-221:1990, MOD) IEC 60050-801 International Electrotechnical Vocabulary - Chapter 801: Acoustics and electroacoustics Note: GB/T 2900.86-2009, Electrotechnical terminology - Acoustics and electroacoustics (IEC 60050-801:1994, IDT) IEC 60404-8-7 Magnetic materials - Part 8-7: Specifications for individual materials - Cold-rolled grain-oriented electrical steel strip and sheet delivered in the fully-processed state Note: GB/T 2521.2-2016, Cold-rolled electrical steel delivered in the fully-processed state - Part 2: Grain-oriented steel strip (sheet) (IEC60404-8-7:2008, MOD) 3 Terms and definitions For the purposes of this document, the terms and definitions given in IEC 60050-103, IEC 60050-121, IEC 60050-221, IEC 60050-801, GB/T 3785.1-2023 and the following 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 butterfly loop butterfly curve hysteresis loop of magnetostriction strain versus magnetic polarization along the direction of applied AC magnetic field for a period of magnetization, as illustrated in Figure 1 Example: 3.2 peak-to-peak value λp-p peak-to-peak amplitude of magnetostriction strain along the direction of applied AC magnetic field, taking an absolute value. Note: The peak-to-peak value can be read from the butterfly loop as shown in Figure 1, expressed in μm/m. 3.3 zero-to-peak value λ0-p difference in magnetostriction strain along the direction of applied AC magnetic field between the values at the prescribed peak magnetic polarization and at the zero value of the magnetic polarization, taking a positive or negative value. Note: The zero-to-peak value can be read from the butterfly loop as shown in Figure 1, expressed in μm/m. 3.4 velocity level Lv indicator of magnetostriction velocity comprising all harmonic components of magnetostriction strain of interest, expressed in dB Note: The frequency weighting filter “A” defined in GB/T 3785.1-2023 can be applied to the velocity level resulting as A-weighted velocity level, LvA , expressed in dB. 3.5 acceleration level La indicator of magnetostriction acceleration comprising all harmonic components of magnetostriction strain of interest, expressed in dB Note: The frequency weighting filter “A” defined in GB/T 3785.1-2023 can be applied to the acceleration level resulting as A-weighted acceleration level, LaA, expressed in dB. 4 General principles 4.1 Principle of the method A length change of a test specimen for a base length under an AC magnetic field is measured by means of a single sheet tester and an optical sensor. Magnetostriction characteristics of the material are determined from the length change of the base length of the test specimen for prescribed peak values of the magnetic polarization and at a specified magnetizing frequency. A schematic diagram of a test apparatus is illustrated in Figure 2. The test apparatus consisting of windings, a winding former, a bridge, a yoke, a clamp block, a weight, an end stop, an optical sensor and auxiliary support structures shall be fixed to a vibration-free table. The test apparatus may be assembled on a rigid base plate which is non-magnetic and fixed to the vibration-free table. Note 1: Methods of measurement under an externally applied compressive stress are described in Annex B. The test specimen shall be placed on the bridge inside the following two windings wound on the winding former (see 4.3.3): ——an exterior primary winding (magnetizing winding); ——an interior secondary winding (induced voltage winding). A flux closure shall be made by the yoke placed under the test specimen. The two pole faces shall be in a horizontal plane. The cross-section of the yoke shall be sufficiently large compared to that of the test specimen. Several types of yoke may be used (see 4.3.2). The winding former shall be placed symmetrically between the two pole faces so that the magnetic field is symmetrically distributed within the winding former. The length of the winding former shall be as long as possible. The bridge between the two pole faces shall be placed inside the winding former without touching the winding former. The bridge shall be sufficiently rigid to keep the test specimen on it flat, and the surface on which the test specimen is placed shall be flat and smooth with a low friction film adhered to the surface (see 4.3.4). Both end parts of the bridge shall be held in close contact with the pole faces. The remaining space between the end parts of the bridge and the pole faces shall be filled with a small amount of high vacuum silicone grease whilst keeping the top surface of the bridge strip flat. In order to prevent a formation of large cavities, the grease should be spotted on the pole face in a grid pattern, the bridge is placed, and pressed firmly from the top of a flat glass plate placed on the bridge.

Contents of GB/T 44391-2024