ASTM A889/A889M-14

3.1 This test method may be used to determine the specific core loss, specific reactive power, specific exciting power, inductance permeability, and impedance permeability of flat-rolled magnetic materials over a wide range of inductions and at frequencies up to 400 Hz for symmetrically magnetized test samples.

3.2 These measurements are used by the producer and user of the flat-rolled material for quality control purposes. The fundamental assumption inherent in these measurements is that they can be correlated with the electromagnetic characteristics of a core fabricated from the flat-rolled material.

1.1 This test method covers tests for the magnetic properties of basic flat-rolled magnetic materials at power frequencies (25 to 400 Hz) using a 25-cm Epstein test frame and the 25-cm double-lap-jointed core.

1.2 The magnetic properties of materials are determined from measurements on Epstein core specimens with the core and test coils treated as though they constituted a series-parallel equivalent circuit (Fig. A1.1) for the fundamental frequency of excitation where the apparent parallel inductance, L₁, and resistance, R ₁, are attributable to the test specimen.

1.3 This test method is suitable for the determination of core loss, rms volt-amperes, rms exciting current, reactive volt-amperes, and related properties of flat-rolled magnetic materials under ac magnetization.

1.4 The frequency range of this test method is normally that of the commercial power frequencies 50 to 60 Hz. It is also acceptable for measurements at frequencies from 25 to 400 Hz. This test method is customarily used on nonoriented electrical steels at inductions up to 10 kG [1.0 T] and for grain-oriented electrical steels at inductions up to 15 kG [1.5 T].

1.5 For reactive properties, both flux and current waveforms introduce limitations. Over its range of useful inductions, the varmeter is valid for the measurement of reactive volt-amperes (vars) and inductance permeability. For the measurement of these properties, it is suggested that test inductions be limited to values sufficiently low that the measured values of vars do not differ by more than 15 % (Note 1) from those calculated from the measured values of exciting volt-amperes and core loss.