Numerical Study on AC Loss of HTS Coil with DC Transport Current under External AC Magnetic Field

High temperature superconducting (HTS) coils can produce stronger magnetic fields compared with conventional permanent magnet. Superconducting magnets wound by YBCO coated conductors can be used on high-speed maglev train, wind generator, energy storage, and other applications. In some cases, such as the rotor of the long-stator linear synchronous motor, superconducting magnets carry a DC current under an external AC magnetic field, because of the harmonics of the stator current and the rotor vibration. The AC loss generated by the external AC field is an essential issue for selecting the capacity of the refrigerator. In this paper, a numerical model of a large-scale circular superconducting magnet is built in order to study its AC losses under the external AC magnetic field. Then the AC losses of the DC HTS magnet under external AC field with different amplitudes and frequencies are calculated, and according to the calculation, the change rules of AC loss versus the amplitude and frequency of the magnetic field are obtained.