Experimental and Numerical Study on Stray Loss in Laminated Magnetic Shielding Under 3-D AC-DC Hybrid Excitations for HVDC Transformers

To investigate the stray loss in magnetic shielding components immersed in the 3-D AC-DC hybrid leakage magnetic field, a modified method is presented with the variation of the eddy current loss inside the coil due to the change of the leakage magnetic field taken into account. In addition, a new loss separation model is proposed to estimate the standard iron loss of the grain-oriented (GO) silicon steel sheet under AC-DC hybrid excitations. Furthermore, the material properties were appropriately treated based on the simplified model of laminated magnetic shielding for efficient numerical calculation. The comparison of field distribution and loss results obtained by experiment and calculation respectively was made, which shows good consistency and thus verifies the effectiveness of the proposed method in this paper. Meanwhile, the stray loss and additional loss in magnetic shielding are analyzed in detail to evaluate the potential threat of AC-DC hybrid excitations on the local overheating of the structural parts in HVDC transformers.