Effects of bridges on AC Losses in Bi-2212 multifilamentary Wire

After heat treatment, bridges formed between the filaments of the Bi ₂ Sr ₂ CaCu ₂ O _x (Bi-2212) superconducting round wires. The impact of these bridges on the current-carrying capacity has not been fully studied and understood, especially the influence of such bridges on the AC loss remains unclear. In this paper, based on the three-dimensional finite element method, numerical simulation studies are conducted using the Kim model and the power law model. Within the frequency range of 50 to 100,000 Hz, and under the condition where the transport current is I _c multiplied by 0.1 to 1, the influence mechanism of the bridging and connection degree of the Bi-2212 filaments on the AC loss is investigated. When the transport current is less than 0.5 times the value of I _c , compared with the ideal Bi-2212 multifilamentary wire without bridging, the bridges hardly affect the magnitude of AC loss. However, when the transport current is greater than 0.5 times value of I _c , the AC loss will rises significantly. As the volume of the bridge structure increases, the AC loss will increase by almost more than 10 times. Furthermore, when large current is transmitted in the low-frequency range, the AC loss will significantly increase due to the presence of the bridge. However, as the frequency increases, the AC loss gradually decreases and eventually approaches the AC loss value of the ideal Bi-2212 multifilamentary wire without the bridges. It suggests that for large current transmission, high frequency can alleviate the impact on the bridge.