Magnetic flux density maps caused by DC, AC and remanence currents around artificial defects in Bi-2223/Ag tapes

Masti, M.; Lehtonen, J.; Perala, R.; Mikkonen, R.

doi:10.1016/s0921-4534(02)02105-6

Cited by 5 publications

(5 citation statements)

References 8 publications

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“…The maximum sample length due to the dimensions of the magnetometer system holder is 70 mm, but the measurable length is limited to 50 mm due to current transfer length demands. The current transfer length of <1.0 mm at dc and about 1.5 mm at 50 Hz ac has been measured in silver sheathed tapes, but an alloyed sheath can increase it [18,19]. Therefore, the current transfer to the superconducting filaments cannot be guaranteed until 5-10 mm from the current contacts.…”

Section: Hall Sensor Magnetometermentioning

confidence: 99%

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Hall sensor magnetometer for ac characterization of high temperature superconducting tapes

Masti

Lehtonen

Perala

et al. 2005

Meas. Sci. Technol.

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During the last five years, the ac performance of high temperature superconductor (HTS) tapes has been under intense development due to the need of practical applications. In order to measure and understand the current density distributions inside these tapes, several methods have already been developed. However, no system has been able to give the time dependent, spatial distribution of the magnetic flux density at a selected distance above the HTS tape carrying any cyclic current signal. In this paper, such a system operating at a frequency range of 0–400 Hz is presented, and possible error sources are extensively investigated. Post-processing of the measured data is explained in detail and error analysis of several example measurements is given. Measurements with HTS and copper samples are compared in order to demonstrate the usefulness of the system.

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Section: Hall Sensor Magnetometermentioning

confidence: 99%

“…These cases are denoted as ac maps, dc maps and remanence maps, accordingly. It has been shown that the most valuable data are obtained when all these three different measurements are combined [19,20]. With the 3D Hall sensor it is also possible to measure maps of B x and B y components.…”

Section: Hall Sensor Magnetometermentioning

confidence: 99%

Hall sensor magnetometer for ac characterization of high temperature superconducting tapes

Masti

Lehtonen

Perala

et al. 2005

Meas. Sci. Technol.

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“…A measurer must know that in the measurement region the current is already flowing in the superconducting region with an adequate accuracy [8]. The measured electric field and equation (32) can be used to determine if the required I CTL criterion is fulfilled in the investigated region.…”

Section: Definition Of Current Transfer Lengthmentioning

confidence: 99%

Current transfer length revisited

Stenvall¹,

Korpela²,

Lehtonen³

et al. 2006

Supercond. Sci. Technol.

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We constructed a model to estimate analytically the current transfer from a matrix to a superconducting region through a highly resistive barrier layer. Also, a numerical model was formulated in order to study the current transfer when the superconducting region has nonlinear resistivity. Because so far the definition for current transfer length (CTL) has not been well established we propose a definition which introduces a method to determine the CTL corresponding to a chosen criterion. Two possible criteria are suggested. One relates to electric field and the other to current in the superconducting region. As a consequence this paper gives an analytical formula which can be used for example in a short-specimen measurement to determine the disposable measurement area. As examples, the different CTL criteria were computed with different resistivities in the superconductor. Also, analytical and numerical models were compared. The analysis was carried out for the possible general structure of future MgB 2 conductors: superconductor, barrier layer and matrix metal. According to the results, the presented analytical model is a useful tool in determining the current transfer length when the barrier layer contact resistance is at least 25 μ mm 2 . Otherwise the presented numerical model must be used.

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“…The critical state model predicts that at subcritical currents there is a current free region inside the conductor. The critical-state-like current penetration creates a flat region in the measured B z -profiles in the middle of the tape [18]. The current of full penetration, I * , corresponds to the current amplitude at which the flat area disappeared completely.…”

Section: Hall Sensor Magnetometrymentioning

confidence: 99%

“…The magnetic flux density component B z perpendicular to the tape broad face was measured on the conductor carrying a transport current. A more detailed description of the system can be found from [18].…”

Section: Hall Sensor Magnetometrymentioning

confidence: 99%

Characterization of low AC loss elementary and assembled BSCCO conductors

Lehtonen¹,

Masti²,

Joronen³

et al. 2005

Supercond. Sci. Technol.

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A European consortium has progressed towards elementary and assembled conductors viable for AC applications in the project ACropolis. The main goal was to achieve low AC losses and high critical current densities in tapes developed for AC coils, transformers and cables. In order to verify the performance of tapes an extensive characterization programme was carried out. The dependence of critical current and AC losses on the parameters of the tape manufacturing process were scrutinized. Furthermore, SEM-EDX and DTA/TG analyses were performed to study the material microstructure, and the diffusion coefficient of oxygen through different matrix metals was measured. The homogeneity of the tapes was verified with magnetic knife and Hall sensor experiments. Transport current measurements were performed at different mechanical stress conditions and also the distribution of critical current along long tapes was determined with a quasi-continuous four-point measurement. The results confirmed that the low AC loss conductors can be produced on an industrial scale and they are competitive in power engineering applications.

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Magnetic flux density maps caused by DC, AC and remanence currents around artificial defects in Bi-2223/Ag tapes

Cited by 5 publications

References 8 publications

Hall sensor magnetometer for ac characterization of high temperature superconducting tapes

Hall sensor magnetometer for ac characterization of high temperature superconducting tapes

Current transfer length revisited

Characterization of low AC loss elementary and assembled BSCCO conductors

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