ASTM A932-01(R2019) pdf free download

ASTM A932-01(R2019) pdf free download.Standard Test Method for Alternating-Current Magnetic Properties of Amorphous Materials at Power Frequencies Using Wattmeter-Ammeter- Voltmeter Method with Sheet Specimens
1. Scope
1.1 This test method covers tests for various magnetic properties of flat-cast amorphous magnetic materials at power frequencies (50 and 60 Hz) using sheet-type specimens in a yoke-type test fixture. It provides for testing using either single- or multiple-layer specimens. N OTE 1—This test method has been applied only at frequencies of 50 and 60 Hz, but with proper instrumentation and application of the principles of testing and calibration embodied in the test method, it is believed to be adaptable to testing at frequencies ranging from 25 to 400 Hz. 1.2 This test method provides a test for specific core loss, specific exciting power and ac peak permeability at moderate and high flux densities, but is restricted to very soft magnetic materials with dc coercivities of 0.07 Oe [5.57 A/m] or less. 1.3 The test method also provides procedures for calculating ac peak permeability from measured peak values of total exciting currents at magnetic field strengths up to about 2 Oe [159 A/m]. 1.4 Explanation of symbols and abbreviated definitions appear in the text of this test method. The official symbols and definitions are listed in Terminology A340. 1.5 This test method shall be used in conjunction with Practice A34/A34M. 1.6 The values stated in either 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 ofthe other. Combining values from the two systems may result in noncon- formance with this standard. 1.7 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 appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use.
4. Significance and Use
4.1 This test method provides a satisfactory means of determining various ac magnetic properties of amorphous magnetic materials. It was developed to supplement the testing of toroidal and Epstein specimens. For testing toroidal speci- mens of amorphous materials, refer to Test Method A912/ A912M. 4.2 The procedures described herein are suitable for use by manufacturers and users of amorphous magnetic materials for materials specification acceptance and manufacturing control. N OTE 2—This test method has been principally applied to the magnetic testing of thermally, magnetically annealed, and flattened amorphous strip at 50 and 60 Hz. Specific core loss at 13 or 14 kG [1.3 or 1.4 T], specific exciting power at 13 or 14 kG [1.3 or 1.4 T], and the flux density, B, at 1 Oe [79.6 A/m] are the recommended parameters for evaluating power grade amorphous materials.
5. Interferences
5.1 Because amorphous magnetic strip is commonly less than 0.0015 in. [0.04 mm] thick, surface roughness tends to have a large effect on the cross-sectional area and the cross section in some areas can be less than the computed average. In such cases, the test results using a single-strip specimen can be substantially different from that measured with a stack of several strips. One approach to minimize the error caused by surface roughness is to use several strips in a stack to average out the variations. The penalty for stacking is that the active magnetic path length of the specimen stack becomes poorly defined. The variation of the active length increases with each additional strip in the stack. Moreover, the active length for stacked strips tends to vary from sample to sample. As the stack height increases, the error as a result of cross-sectional variations diminishes but that as a result of length variations increases with the overall optimum at about four to six layers. The accuracy for stacked strips is never as good as for a single layer of smooth strip. 5.2 Some amorphous magnetic materials are highly magne-tostrictive. This is an additional potential source of error because even a small amount of surface loading, twisting, or flattening will cause a noticeable change in the measured values.
6. Basic Test Circuit
6.1 Fig. 1 provides a schematic circuit diagram for the test method. A power source of precisely controllable ac sinusoidal voltage is used to energize the primary circuit. To minimize flux-waveform distortion, current ratings of the power source and of the wiring and switches in the primary circuit shall be such as to provide very low impedance relative to the imped- ance arising from the test fixture and test specimen. Ratings of switches and wiring in the secondary circuit also shall be such as to cause negligible voltage drop between the terminals ofthe secondary test winding and the terminals of the measuring instruments.