Magnetization and demagnetization studies of a HTS bulk in a symmetrical iron core
Résumé
In order to design and understand some new electrical applications using superconducting permanent magnets, which have some very high trapped magnetic field, it is necessary to study their demagnetization.
In a motor, for example, the magnets are submitted to a variable magnetic field. This could demagnetize the superconducting magnets which are themselves magnetized by a variable magnetic field.
So we propose new experimentation in order to study the influence of an alternating external magnetic field on superconducting magnets. Our experiments are carried out in a liquid nitrogen bath, and we use YBCO superconducting bulk pellets. During the first step, we have magnetized a superconducting bulk in an iron core by a PFM method. The iron core represents the equivalent magnetic circuit of an electrical motor. After that, an alternative magnetic field with several significant amplitudes, more than 10% of the trapped magnetic field, is applied to the magnetized superconducting magnet. The experiment is repeated for several frequencies, and the trapped magnetic field is observed at the center and at the edge of the pellet's surface by using Hall sensors.
We will show that, in our case, there was no significant decrease of the trapped magnetic field even after several cycles or high frequencies. This is an important result and a good omen for future potential applications referred.