ASTM A804-04(R2021) pdf free download

ASTM A804-04(R2021) pdf free download.Standard Test Methods for Alternating-Current Magnetic Properties of Materials at Power Frequencies Using Sheet-Type Test Specimens
4. Significance and Use
4.1 Materials Evaluation—These test methods were devel- oped to supplement the testing of Epstein specimens for applications involving the use of flat, sheared laminations where the testing of Epstein specimens in either the as-sheared or stress-relief-annealed condition fails to provide the most satisfactory method of predicting magnetic performance in the application. As a principal example, the test methods have been found particularly applicable to the control and evaluation of the magnetic properties of thermally flattened, grain-oriented electrical steel (Condition F5, Specification A876) used as lamination stock for cores of power transformers. Inasmuch as the test methods can only be reliably used to determine unidirectional magnetic properties, the test methods have limited applicability to the testing of fully processed nonori- ented electrical steels as normally practiced (Specification A677). 4.2 Specification Acceptance—The reproducibility of test results and the accuracy relative to the 25-cm [250-mm] Epstein method of test are considered such as to render the test methods suitable for materials specification testing. 4.3 Interpretation of Test Results—Because of specimen size, considerable variation in magnetic properties may be present within a single specimen or between specimens that may be combined for testing purposes. Also, variations may exist in test values that are combined to represent a test lot of material. Test results reported will therefore, in general, repre- sent averages of magnetic quality and in certain applications, particularly those involving narrow widths of laminations, deviations in magnetic performance from those expected from reported data may occur at times. Additionally, application of test data to the design or evaluation of a particular magnetic device must recognize the influence of magnetic circuitry upon performance and the possible deterioration in magnetic prop- erties arising from construction of the device.
7. Apparatus
7.1 The test circuit shall incorporate as many of the follow- ing components as are required to perform the desired mea- surements. 7.2 Yoke Test Fixture—Fig. 2 and Fig. 3 show line drawings ofa single-yoke fixture and a double-yoke fixture, respectively. A double-yoke fixture is preferred in this method but a single-yoke fixture is permitted. Directions concerning the design, construction, and calibration of the fixture are given in 7.2.1, 7.2.2, Annex A1, and Annex A2. 7.2.1 Yoke Structure—Various dimensions and fabrication procedures in construction are permissible. Since the recom- mended calibration procedure provides correlation with the 25-cm [250-mm] Epstein test, the minimum inside dimension between pole faces must be at least 22 cm [220 mm]. The thickness of the pole faces should be not less than 2.5 cm [25 mm]. It is recognized that pole faces as narrow as 1.9 cm [19 mm] are being used with nickel-iron yoke systems with good results. To minimize the influences of coil-end and pole-face effects, the yokes should be longer than the recommended minimum. For calibration purposes, it is suggested that the width of the fixture be such as to accommodate a specimen of at least 36-cm [360-mm] width which corresponds to the combined width of twelve Epstein-type specimens. Should the fixture width be less than 36 cm [360 mm], it will be necessary to test each calibration specimen in two parts and average the results. 7.2.2 Test Windings—The test windings, which shall consist of a primary (exciting) winding and a secondary (potential) winding, shall be uniformly and closely wound on a nonmagnetic, nonconducting coil form and each shall span the greatest practicable distance between the pole faces ofthe yoke fixture. It is recommended that the number of turns in the primary and secondary windings be equal. The number ofturns may be chosen to suit the instrumentation, mass of specimen and test frequency.