67 – Analysis of AC Loss in a Superconductor

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Application Note / Model Data

Overview

When superconductors are in the superconducting state, in which temperature, magnetic field and current become lower than a critical value, its electrical resistance becomes zero. Although superconducting wire rod requires a cooling system to maintain a low-temperature state, having features such as high current density and extremely low loss, it has a lot of advantages in terms of energy and environment. The electrical resistance in the superconductor becomes zero, when DC is applied, but when AC is applied, loss is caused in a superconductor. In JMAG, the AC loss in a superconductor can be obtained.
This note presents the use of magnetic field analysis to obtain the AC loss in a superconductive filament.

AC Loss

Table 1 shows the average AC loss per meter in the longitudinal direction when applied current is between 50 and 80 % of critical current. Figure 1 and Figure 2 show the AC loss over time.
The AC loss caused by magnetic hysteresis inside the superconductor varies with the amplitude of the applied current.

Current Density Distribution

Figure 3 and Figure 4 show the current density distribution of a normal conductor and a superconductor, respectively , when 80% of critical current is applied. The +Z direction is a positive direction of applied current amplitude.

The applied current amplitude is maximized at 0.025 seconds. At this time, the current flows uniformly in the normal conductor. Meanwhile, the current flows toward both sides in the superconductor. This non-uniform current distribution is the cause of the greater loss.

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