Magnetization process in electrical steel sheets

变压器、发电机和电动机中的能量损失，其中使用电工钢板，强烈地由这些钢板中的磁畴决定。因此，理解的损失机制和减少战略的发展需要通过显微成像的域和磁化过程的基础研究。然而，为了降低涡流效应，片被不透明的绝缘涂层覆盖，这使得不可能通过光学手段直接观察畴结构。对于磁光克尔显微镜，必须去除该覆盖层，并且必须仔细抛光表面，这不幸地导致磁特性和畴结构的急剧变化。通过使用最近开发的新一代磁光指示膜（MOIF），它被放置在涂层板的顶部，并间接揭示了底层的域分布，情况发生了很大的变化：域现在可以在绝缘涂层的存在下成像，具有足够的分辨率，甚至在时间分辨的方式通过单次拍摄成像在电源频率。此外，指示膜允许在晶粒边界处对磁极进行成像，从而可以研究晶粒边界对于通量传输的作用。在这个项目中，MOIF薄膜的潜力将被用来获得在工作条件下电工钢的准静态和动态磁化过程的更深入的了解。我们的目标是从根本上了解能量损失的微观来源，为电气设备和机器中有针对性的最小化损失提供基础。

The energy losses in transformers, generators and electro-motors, where electrical steel sheets are utilized, are strongly determined by the magnetic domains in these sheets. The understanding of the loss mechanisms and the development of strategies for their reduction therefore requires fundamental studies of the domains and magnetization processes by microscopic imaging. To lower eddy current effects, however, the sheets are covered by non-transparent insulation coatings that make a direct observation of the domain structure by optical means impossible. For magneto-optical Kerr microscopy this cover layer has to be removed and the surface has to be carefully polished, which unfortunately leads to drastic changes of the magnetic properties and domain structure. By using a recently developed new generation of magneto-optical indicator films (MOIF), which are placed on top of coated sheets and which indirectly reveal the underlying domain distribution, the situation has considerably changed: the domains can now be imaged in the presence of insulation coatings with a sufficient resolution and even in a time-resolved manner by single-shot imaging at power frequencies. The indicator films furthermore allow for the imaging of magnetic poles at grain boundaries, making it possible to study the role of grain boundaries for the flux transport. In this project the potential of the MOIF films shall be used to obtain a deeper understanding of the quasistatic and dynamic magnetization processes in electrical steel under working conditions. The goal is a fundamental understanding of the microscopic sources of energy loss to provide a basis for a targeted minimization of loss in electrical devices and machines.