Local Non-contact Evaluation of the ac Magnetic Hysteresis Parameters of Electrical Steels by the Barkhausen Noise Technique

The potential of the magnetic Barkhausen noise method for local repeatable testing of the magnetic hysteresis properties of electrical steels was investigated. Strips of non-oriented and grain-oriented electrical steels were magnetized by a single yoke through 0–10 mm air gaps. The measurements were performed at standard ac conditions: 50 Hz sine induction waveform with different amplitudes. A vertically mounted array of three Hall sensors was used for the direct measurement of the surface magnetic field. The Barkhausen noise was detected locally by a surface-mounted pancake coil. The simultaneous measurement of the actual sample field makes it possible to stabilize a recently introduced parameter, called Barkhausen noise coercivity. This parameter demonstrates strong linear correlations to the hysteresis coercive force and to the hysteresis losses measured by the standard single sheet tester.