Abstract
Nanocrystalline alloys are now widely used in high frequency electromagnetic applications such as high frequency transformers and chokes, while it’s two-dimensional properties are seldom investigated. The nanocrystalline sample can be extremely brittle after annealed and crystallized which is very difficult to measure the properties by traditional method in 2D cases. The magnetic properties of nanocrystalline alloys under rotating field are measured and discussed in this paper. By combining the needle probe technique and the H-coil method, the magnetic flux density B and the magnetic field strength H in the sample can be measured. Finally, the modified B-H sensor is calibrated by the Helmholtz coils and the sensitivity of measuring B and H can achieve 4.3 mV/T and 30 μV/A/m respectively.
Highlights
To meet the demand of energy saving and emission reduction, high frequency and high power density devices have attracted significant attention in recent years.[1,2] Magnetic characterization of such materials helps engineers design and develop efficient electrical machines and devices as well as scientists work in this field
By measuring the vector magnetic flux density B and the magnetic field strength H, the specific loss per cycle can be calculated through the field-metric method.[6]
0.03 at is thickness of nanocrystalline sample for needles probe, and the thickness of flat frame of H coil. bd is the distance between two needle probes, and the width for the H coil. cφ is the diameter of the probe for needle probes, and the diameter of enameled wires for H coil. dS is the sensitivity of the needle probes and the H coil
Summary
To meet the demand of energy saving and emission reduction, high frequency and high power density devices have attracted significant attention in recent years.[1,2] Magnetic characterization of such materials helps engineers design and develop efficient electrical machines and devices as well as scientists work in this field. When annealed by a transverse field, the nanocrystalline tapes can show excellent broadband magnetic properties and even lower energy loss than the ferrite at high frequencies.[3] But the characterization of nanocrystalline alloys is restricted in the so-called one-dimensional method, standardized in the IEC60404-6, which can measure the magnetic properties only along the casting direction of the nanocrystalline sample while it can’t reflect any information about the anisotropy properties. Several researchers have moved to the topic of measurements of 2D magnetic properties of electrical steels for decades of years.[4] In recent years, the vector magnetic properties of Fe-based amorphous sheet have been tested under the alternating and rotating fields while the maximum testing frequency is 750 Hz far from the working condition of the high frequency applications.[5] But such measurement of nanocrystalline sample is restricted because the tapes become very brittle after the annealing process.
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