Harmonic

Harmonics are harmonics of the mains frequency caused by non-linear electronic loads such as power supply units, UPS systems, motor controllers and other electronic devices. These harmonics occur because electronic devices are often unable to process alternating current (AC) without distortion. Instead, they generate multiples of the mains frequency, which is typically 50 Hz. The most common harmonics are the 3rd harmonic (150 Hz), the 5th harmonic (250 Hz) and the 7th harmonic (350 Hz).