ABSTRACT
Following the discussion on core materials and structures, the components of no-load loss, generated by core material like hysteresis and eddy current losses, by structural features such as corner of core, and by production features like holes in laminations for stacking alignment, gaps between laminations and burrs, which are inevitable, are investigated. The practical no-load loss calculation method is given followed by examples. The way to estimate extra loss caused by burrs is introduced to help investigations on cases of high-tested no-load losses. Characteristics of exciting current and the calculation method of its magnitude are given followed by examples of two-winding without regulating winding, and with regulating winding plus series transformer. Phenomenon of inrush current is analyzed to estimate the maximum current magnitude. Attempt on flux density in core under quasi-DC current is conducted to aid study on effect of geomagnetically induced current on transformer. Finally, the performances of gapped core used in preventive auto transformer and reactor with a calculation example are presented.
