報告題目：Low AC loss in the REBCO stator of a 1 MW motor for aviation
報告人：Dr. Enric PARDO
報告地點：騰訊會議ID:358 292 294
Dr. Enric PARDO is the head of the Department of Superconductors in the Institute of Electrical Engineering of the Slovak Academy of Sciences (IEE SAS). He received his Master Degree and PhD in Physics in 1999 and 2004, respectively, from the Autonomous University of Barcelona (UAB).
He is highly experienced in numerical modelling of electro-magnetic properties of superconductors, although he is also internationally recognized for modelling demagnetizing effects in magnetic materials. Before achieving a permanent position in IEE SAS, where he works since 2010, he was teacher assistant in UAB and made post-doctoral stays in the University of Cambridge (2005), Vienna University of Technology (2009) and IEE SAS. He has over 20 years’ experience in superconductivity, he is author of more than 100 articles with more than 2400 citations, and has h-index 29 from Web of Knowledge. He received the IEEE Van Duzer Prize and IEEE Senior Member recognition.
Hybrid-electric distributed propulsion can drastically reduce emissions in commercial flights, meeting the European Union emission reduction goals of 75 % in CO2, 90 % in NOx, and 65 % in noise by 2050. Superconducting electric motors and generators are very promising for this application, thanks to their high power-over-weight ratio. Full superconducting motors can be achieved by using REBCO high-temperature superconductors in the stator and stacks of tapes in the rotor, acting as strong permanent magnets. In this talk, first we analyze the effect of ripple fields in the stacks of the rotor, which reduce their generated magnetic field. Afterwards, we discuss the AC loss in the stator winding. For this purpose, we use innovative in-house software for Finite-Element-Method (FEM) calculations, based on the Minimum Electro-Magnetic Entropy Production (MEMEP) and, for the stator coils, we also perform measurements at 25 K.
For the stacks in the rotor, we have realized that useful predictions require modeling of millions of ripple field cycles. In order to achieve this, we use an effective non-linear resistivity based on dynamic magneto-resistance, outperforming conventional FEM modeling by 4 orders of magnitude. We have found that although stacks could trap higher fields than bulks, they are more sensitive to ripple fields after long operation times. In order to avoid this drawback for stacks, we propose to solder tapes in pairs.
For the stator, modeling results show that, due to the distributed winding geometry of the stator, using parallel-tape conductors with tapes isolated along their length reduces the AC loss to the theoretical limit of ideally transposed cables. Thanks to this and other strategies, REBCO stators are able to experience very low AC loss without striations or using complex transposed wires. Other factors, such as tape homogeneity, may play a more important role. In addition, measurements show that the residual magnetism of the Hastelloy(R) substrate causes an essential contribution to the AC loss at the coil self-field, and possibly also in the motor configuration.