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In order to study and analyze the rotating magnetic properties for nanocrystalline material, an improved 2-D high-frequency magnetic properties tester with step-shaped excitation windings and composite sensing structure is designed and modeled. Magnetic concentration and core poles optimization are performed in 2-D tester construction, which can generate relatively uniform and strong magnetic field in the testing area. By using the composite sensing structure of sensing coil combined with needle probe method, $B$ and $H$ signals can accurately be detected. Meanwhile, feedback control algorithm and harmonic compensation are established to obtain the desired magnetization curves and improve the measurement precision. [ABSTRACT FROM AUTHOR]

The total noise level of transformers is mainly influenced by harmonics in load current. The reasons are the interaction of harmonics with large load current at power frequency and the rising sound radiation efficiency with frequency. It is noted that the dynamic vibration behaviors under load harmonics operation are important to decrease the equipment noise. This paper mainly studies the vibration noise effects of three-phase three-leg transformer with the load of wireless power transfer (WPT) system, which would bring harmonics in the load current. Accelerometer sensors were arranged on the surface of the cores and windings of the transformer. Then, the vibration was measured in different positions of a transformer under the power of WPT system from 0 to 20 kW. The spectral distribution of vibration was obtained through the fast-Fourier transform analysis of the acquisition signals. The experimental results with and without PWT load imply that the harmonics in load-current have great effect on the vibration noise. It is to conclude that the main several harmonics of load current should be eliminated to reduce the vibration noise level. [ABSTRACT FROM AUTHOR]

A new closed-loop magnetic current sensor is presented in this paper. The sensor consists of two toroidal magnetic cores. One core works in fluxgate principle for the measurement of dc and low-frequency ac, and the other one is used as a current transformer for higher frequency application. Based on the simulation results, a prototype was designed, and the test results have a good agreement with the simulation results. The closed-loop configuration with a magnetic core and a feedback winding in the sensor improved the sensitivity of the sensor, eliminated the offset and drift related to temperature, and greatly reduced the error caused by magnetic hysteresis phenomenon. It can measure currents up to 20 A, with an accuracy of 0.5%, and a 50 kHz small signal bandwidth. [ABSTRACT FROM PUBLISHER]