Harmonics

The increase of equipment with non-linear characteristics (e.g. power electronics), which withdraw a non-sinusoidal current from the electrical network with sinusoidal voltage, leads to higher harmonics load.Harmonics are currents with an integral multiple of the electrical network frequency (50 or 60 Hz). In practice, currents up to the 50th harmonic may be significant.The 5th (250 Hz), 7th (350 Hz), 11th (550 Hz) and 13th (650 Hz) harmonics have the highest importance for electrical network and equipment. However, the 3rd and 9th harmonics are likewise becoming more significant.The total harmonics distorsion is indicated in percentage (%) THDU or THDI. The higher the THDU or THDI, the higher is the electrical network and equipment load

 

Negative effects of harmonics

Harmonic currents represent an additional load on all electrical equipments.
The consequences may be:


 

  • Increased energy costs resulting from power/heat losses

  • Faults in communication and control systems

  • Shaking moments and irregular operation of electric equipment

  • Reduced lifetime

  • Overloading of electric equipment

  • Deficient product and process quality

  • Higher CO2 emissions