Standard Guide for Measuring Power Frequency Magnetic Properties of Flat-Rolled Electrical Steels Using Small Single Sheet Testers
4.1 Materials Evaluation—Small single sheet testers were developed to supplement the testing of Epstein specimens for various applications. They are especially appropriate for determining the magnetic properties of samples when insufficient material is available for preparation of an Epstein specimen. Although the small specimen size is attractive, the precision of the small sheet testers is not expected to be as good as that of the test method Test Method A343/A343M. Small sheet testers are frequently used to measure the properties of both fully processed and semiprocessed nonoriented and magnetic lamination steels. Specimens of semiprocessed steels are normally subjected to an appropriate quality development anneal prior to testing. Small sheet testers may also be used to evaluate oriented electrical steels in either the as sheared or stress-relief annealed condition.
1.1 This guide covers procedures for interpreting the specific core loss and peak permeability determined using small single-sheet test systems. It is limited to single-sheet test systems that require a test specimen or coupon be cut from the material being tested and are designed such that the entire width of that test specimen is magnetized during testing.
1.2 This guide is primarily intended for measurements of the magnetic properties of flat-rolled electrical steels at frequencies of 50 Hz or 60 Hz under sinusoidal flux conditions.
1.3 This guide includes procedures to provide correlation with the 25-cm Epstein test method (Test Method A343/A343M).
1.4 The range of magnetic flux densities is governed by the properties of the test specimens and the instruments and test power source. Nonoriented electrical steels may be tested at magnetic flux densities up to about 16-kG [1.6T] for core loss. The maximum magnetic field strength for peak permeability testing is limited by the current carrying capacity of the magnetizing winding and the test power source. Single sheet testers are typically capable of testing at magnetic field strengths up to 50 Oe [4000 A/m] or more.
1.5 Within this guide, a small single sheet tester (small SST) is defined as a magnetic tester designed to test flat, rectangular sheet-type specimens. Typical specimens for these testers are square (or nearly so). The design of the small SST test fixture may be small enough to accommodate specimens about 5 by 5 cm or may be large enough to accommodate specimens about 36 by 36 cm. Specimens for a particular SST must be appropriate for the particular test fixture.
1.6 This guide covers two alternative test methods: Method 1 and Method 2.
1.6.1 Method 1 is an extension of Method 1 of Test Method A804/A804M, which describes a test fixture having two windings that encircle the test specimen and two low-reluctance, low-core loss ferromagnetic yokes that serve as flux return paths. The dimensions of the test fixture for Method 1 are not fixed but rather may be designed and built for any nominal specimen dimension within the limits given in 1.5. The power loss in this case is determined by measuring the average value of the product of primary current and induced secondary voltage.
1.6.2 Method 2 covers the use of a small single sheet tester, which employs a magnetizing winding, a magnetic flux sensing winding, and a magnetic field strength detector. The power loss in this case is determined by measuring the average value of the product of induced secondary voltage and magnetic field strength.
1.6.3 The calibration method described in the annex of this guide applies to both test methods.
1.7 The values and equations stated in customary (cgs-emu and inch-pound) or SI units are to be regarded separately as standard. Within this standard, SI units are shown in brackets. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with this standard.
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory requirements prior to use.
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