Harmonics are periodic distortions of voltage, current, or electricity sine waves. Harmonics in electricity distribution devices are often brought on by non-linear loads such as switched manner dc electric power provides and adjustable speed motor drives.Không ?? v?n n?n "?n ch?n" ?e d?a th? thao Vi?t Nam Ch? trong vòng ch?a ??y n?a n?m, th? thao