Harmonics are periodic distortions of voltage, existing, or electric power sine waves. Harmonics in energy distribution units are sometimes due to non-linear hundreds such as switched method dc electric power materials and adjustable velocity motor drives.K?t qu? x? s? mi?n Nam bao g?m 9 gi?i t? gi?i ??c Bi?t ??n gi?i Tám, t??ng ???ng v?i eighteen