Harmonics are periodic distortions of voltage, recent, or energy sine waves. Harmonics in electrical power distribution systems are frequently brought on by non-linear loads such as switched manner dc energy supplies 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 Vi?