What are Harmonics? 

Harmonic voltages (harmonics) have the potential to cause equipment malfunction, overheating and hardware damage. They are a result of the distortion of normal electrical current caused by non-linear electrical loads. These non-linear power supplies draw current in high-amplitude short pulses that create significant distortion in the electrical current and voltage wave shape – harmonic distortion, measured as total harmonic distortion (THD). 

The distortion travels back into the power source and can affect other equipment connected to the same source. Most power systems will experience problems when harmonics become a significant component of the overall load. 

Harmonic currents are generated by non-linear loads like 

• LED and CFL lighting, 
• Switch Mode Power Supply (SMPS) units (computers, PLCs), 
• Variable frequency drives used with motors 
• UPS 
• Arc furnaces & SCR temperature controllers Battery chargers & Rectifiers 

What Problems Are Caused by Harmonics? 

Harmonic voltages in electricity supply can cause equipment and machinery to behave erratically or entirely malfunction. However, it can go completely undetected and misdiagnosed.   

Effects of Harmonics 

Cause 

• Rise of the total current harmonic distortion (THDi%) 
• Unwanted tripping of circuit breakers and residual current devices 
• Increase in transformer temperature 
• Decrease in UPS performance 
• Decrease in motor performance 
• Overheating of cable and switchboards 

Effects 

• Current increase in conductors, temperature increase in conductors, possible insulation loss in conductors, malfunction in PLC. 
• Power cuts in production lines 
• Premature ageing of the transformer 
• Need to expand UPS 
• Premature ageing of motors 

Problems 

• Economic losses due to production downtimes
• Extra costs in maintenance 
• Extra costs in installation, risk of production downtime and data loss  

How does an Active Harmonic Filter Work? 

Active Harmonic Filters (AHF) are filters and the perfect comprehensive solution to power quality problems with the grid, such as harmonics, reactive power, and three-phase load imbalance. Active harmonic filters can be used to filter out harmonics in the power system significantly below the filter’s switching frequency. 

The active harmonic filter cleans out higher and lower-order harmonics in an electrical system. The process is also known as harmonic mitigation. 

Benefits of Active Harmonic Filters 

• Reduces the Harmonics in compliance with IEEE 519:2014 
• Maintains Unity PF operation 
• Ensures Load balancing 
• Reduces overloading and overheating of Neutral conductor 
• Help in avoiding the nuisance tripping of switchgear caused due to harmonics 
• Compensates neutral current (with 3Ph4W option only) 
• Lowers the energy Bill