[W-MA-48] Analyses of Higher Harmonics Copper Loss and Improvements Through Design Changes

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Overview

1. Background
Increasing the accuracy of a loss analysis for a magnetic field analysis becomes an important issue. Various factors cause losses to diverge from their theoretical state, and they typically tend to be treated as stray load loss. One of these factors that stand out is alternating current copper loss(AC copper loss). The following types of AC copper loss phenomena are caused by the interlinking of magnetic flux with time variations in conductors such as coils.
 - Skin effect
  Phenomenon in which current concentrates on the surface of a conductor due to the skin effect from eddy currents.
 - Proximity effect
  Phenomena occurring in addition to the skin effect from cases such as multiple conductors, leakage flux interlinking from magnetic material, and other contributing factors.
These phenomena cause currents to concentrate inside conductors, and the entire area of cross-sectional area of a conductor cannot be fully used in comparison with the unchanging direct current of a magnetic field. In other words, resistance increases compared to direct current, and copper loss increases when attempting to run the same current. This is alternating current copper loss, one of the contributing factors of stray load loss in electric machines, causing efficiency to decrease.
Especially in today’s motors, the decreasing of size (improved lamination factor and smaller coil ends), improvement of heat dissipation, and the improvement of production requires an increased adoption of square and rectangular wires, such as segment coils and edge-wise coils [1], and an understanding of the causes of AC copper loss in order to take countermeasures through design changes is necessary.

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