What is harmonics in electrical system and how to minimize that ?

Harmonics are any “Non-Linear” Current or Voltage in an electrical distribution system. Harmonics are commonly produced by a device that rectifies AC Voltage into a DC Voltage. Common Harmonic producing devices are VFDs, Lighting, and Computers. To create a DC voltage from an AC sine wave a Bridge Rectifier circuit is used to maintain a DC Charge on a capacitor.

Current Harmonics

Bridge rectifier circuits produce current harmonics. Current Harmonics do have an affect on the electrical equipment supplying harmonic current to the device (transformers, conductors). Current Harmonics can cause issues with distribution equipment with has to handle the current from the utility transformer all the way down to the device, but generally don’t affect other equipment connected to the electrical system. Harmonic currents can cause excessive heating to transformers.

Voltage Harmonics

Voltage Harmonics can affects sensitive equipment throughout your facility. Voltage Harmonics arise when Current Harmonics are able to create sags in the voltage supply. When any device draws current it creates a voltage dip which is required for current to flow. Current Harmonics create Voltage Harmonics, but the magnitude of the Voltage Harmonics depends on the “Stiffness” of your electrical distribution’s “System Impedance”.

How to reduce Current Harmonics:

1.By adding line chokes or transformer to harmonic producing equipment

2.By using 12-Pulse or 18-Pulse Rectifier circuits instead of 6-Pulse during rectification.

How to reduce Voltage Harmonics:

1.By adding tuned capacitor banks to supply harmonic current

2. By changing  transformer Size/Impedance.