AbstractThe author recently noticed that noise not only contaminates signals, but also heats electronic circuits. This new viewpoint suggests a reason why lithium-ion batteries of a sophisticated new aircraft, a Boeing 787, encountered overheating, or caught fire, because conventional electronic circuits could produce enough noise to heat circuit elements. In order to overcome this issue concerning the DC-line system of the AC-DC converter, it has been practically and theoretically proven that a symmetric three-line（S3L）circuit with both common- and normal-mode filters is excellent for noise reduction. On the other hand, the author identified a common-mode noise in addition to the normal-mode noise at an AC line, several years ago. In order to overcome such problems of an AC-line system as those of a DC-line system, the author recommends the symmetrization and a common-mode filter for the AC-line system of an AC-DC converter. This paper describes how both common- and normal-mode noises could heat electronic circuits based on calculations of three-line circuit theory. Heating occurs along with the coupling of common- and normal modes of a propagation wave type and the reflection of both waves at circuit elements, causing complicated phenomena beyond our understanding based on the conventional circuit theory.