Critical evaluation and limitations of localized flux density measurements in electrical steels

Abstract

Search coils and needle probes are existing experimental sensors that can measure flux distributions in electrical steels. This work investigates and evaluates the limitations of each method, proposes the use of a new modified needle probe method and gives reasons for its improved applicability and relative merits.Index Terms-Electrical steels, flux density measurements, needle probe method, search coil method.

Investigation of the influence of different cutting procedures on the global and local magnetic properties of non-oriented electrical steel

“…Due to these stresses the magnetic properties of the material are deteriorated which can be determined by an integral measurement of the magnetization curve of the bulk material. Previous works tried to identify the local magnetic properties near the cutting edges by using needle probes [1][2][3]. Local magnetic properties after punching have also been investigated with spatially resolved measurements [4] or using a single-sheet-tester with repeatedly cut sheets to determine the influence of the cutting length in relation to the sample volume [5,6].…”

Applicability of local magnetic measurements

“…Modern Hall/GMR elements with extremely high sensitivity are suitable for this task [18,19,[23][24][25]. For the local reading of magnetic response a needle probe for the hysteresis measurement or a pancake coil for the Barkhausen noise testing should be used [15,21,26]. The magnetization conditions must be also controlled locally through the flux waveform, measured by the needle probe, or through the field waveform, determined by the Hall/GMR element/s.…”

2D magnetization of grain-oriented 3%-Si steel under uniaxial stress

“…To meet these challenges, a specially designed magnetic measurement setup is used [10]. It allows combining a uniaxial mechanical load, either compressive or tensile, and two-dimensional magnetic system.…”

“…Both magnetic flux density B and magnetic field strength H are measured locally in the geometrical center of the system and the center of the sample. The flux density is measured by two needle probes, as it is a reliable non-destructive method at sufficient distances between two needle probes [10]. The field strength is measured by H-coils as follows.…”