Standard: ASTM - A347

STANDARD TEST METHOD FOR ALTERNATING-CURRENT MAGNETIC PROPERTIES OF MATERIALS USING THE DIETERLY BRIDGE METHOD WITH 25-CM EPSTEIN FRAME

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Scope:

1. Scope

1.1 This test method provides a test for various magnetic properties of flat-rolled materials, using a 25-cm Epstein test frame and a 25-cm double-lap-jointed core.

1.2 The magnetic properties of materials are determined from bridge measurements on Epstein core specimens with the core and test coils treated as though they constituted a series-parallel equivalent circuit (Fig. Al.2, arm n-q) for the fundamental frequency of excitation where the apparent parallel inductance, Li and resistance, Ri, are attributable to the test specimen.

1.2.1 No impedance bridge can be completely balanced when measuring a loaded Epstein frame. The Dieterly Bridge can be effectively balanced by using a null detector, D, which responds only to the fundamental frequency component of the voltage across the detector branch, m-n, of the bridge circuit.

1.3 This test method is suitable for determination of core loss. PC reactive volt-amperes, Pq, a-c inductance permeability, ┬ÁL, and apparent parallel resistance and inductance of the test specimen.

1.4 This bridge method may be used at commercial power frequencies (50 and 60 Hz) and at audio frequencies up to a limit of 400 Hz. This test method is customarily used on nonoriented electrical steels at induction levels up to 10 kG (1.0 T) and for grain-oriented electrical steels at induction levels up to 15 kG (1.5 T). For core loss measurements only, on these materials, it is useful up to 12 kG (1.2 T) and 16 kG (1.6 T), respectively.

1.5 The Dieterly bridge can be effectively balanced at any induction level in the test material and valuable comparative fundamental frequency data can thereby be obtained which the producer and consumer can use for quality control purposes. At induction levels above 10 kG (1.0 T), Test Method A 343 is the more widely accepted method for core loss and other measurements.

1.6 For reactive properties both flux and current wave forms introduce limitations. Over its range of useful inductions, the bridge method is valid for measurement of inductance permeability and reactive voltamperes (vars). For measurement of these properties, it is recommended that test inductions be limited to inductions sufficiently low that the measured values of vars do not differ by more than 15 % (Note 1) from those calculated from measured values of core loss and exciting voltamperes using Test Method A 343.

NOTE 1--This limitation is placed on this test method in consideration of the nonlinear nature of the magnetic circuit, which leads to a difference between vars based on fundamental frequency components of voltage and current after harmonic rejection and vars calculated directly from rms current, voltage, and watt values when one or more of these parameters is nonsinusoidal.

1.7 Tests may be made for permeability under incremental test conditions (a-c magnetization superimposed upon d-c magnetization) provided the combined effect of biasing field and alternating inductions are limited to values below which excessive distortion and nonsymmetry exists in the magnetizing current.

1.8 This test method shall be used in conjunction with Practice A 34.

1.9 Explanation of terms, symbols, and definitions used may be found in the various sections of this test method. The official list of definitions and symbols may be found in Definitions A 340.

1.10 This standard does not purport to address all of the safety problems, 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 limitations prior to use.

Organization: ASTM International
Document Number: a347
Publish Date: 1985-04-30
Page Count: 8
Available Languages: EN
DOD Adopted: NO
ANSI Approved: NO
Most Recent Revision: YES
Current Version: YES
Status: Inactive

Document History

Document # Change Type Update Date Revision Status
ASTM A347 Change Type: REAP Update Date: 1985-01-01 Revision: 85 Status: INAC

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