Variable Frequency Drives (VFDs) are widely used for controlling motor speed, improving process control, and reducing energy consumption. However, a common drawback of standard VFDs is the introduction of harmonics into the power system—distortions in the electrical current that can harm equipment and reduce efficiency.
This is where Low Harmonic VFD comes in. Designed to minimize harmonic distortion, these drives are essential for facilities that demand high power quality and compliance with international standards.
In this article, we’ll explore what a low harmonic VFD is, how it works, and why it's a critical choice in today’s electrical systems.

???? What Is a Low Harmonic VFD?
A Low Harmonic VFD is a type of variable frequency drive that’s specifically engineered to reduce the amount of harmonic distortion it sends back to the power supply. While standard VFDs often cause Total Harmonic Distortion (THD) levels of 30–50%, a low harmonic VFD can bring this figure down to less than 5%, complying with IEEE-519 and other global standards.
These drives are particularly beneficial in applications where maintaining a clean power supply is critical—such as hospitals, data centers, industrial plants, and commercial buildings.

⚙️ How Do Low Harmonic VFDs Work?
Low harmonic VFDs use various methods to reduce harmonic distortion:
1. Active Front End (AFE)
Uses insulated-gate bipolar transistors (IGBTs) in the rectifier stage.


Allows bi-directional power flow (regenerative braking).


Actively cancels harmonic currents by injecting opposite-phase signals.


2. Multi-Pulse Configurations (12-pulse or 18-pulse)
Uses multiple rectifiers and phase-shifting transformers.


Cancels out specific harmonic orders.


Offers passive harmonic reduction without complex electronics.


3. Passive or Active Filters
External components added to standard VFDs.


Filters out specific harmonics to reduce overall THD.



✅ Benefits of Using a Low Harmonic VFD
???? Improved Power Quality
Low harmonic VFDs help maintain a clean sine wave, reducing interference with other sensitive electronic equipment on the same power line.
????️ Protects Equipment
Lower harmonics mean reduced heating and stress on transformers, motors, cables, and capacitors—leading to longer equipment life.
???? Compliance with Standards
Meets harmonic distortion standards like IEEE-519, which is required in many commercial and industrial installations.
???? Reduces Energy Losses
Harmonics contribute to inefficiencies in power systems. A low harmonic VFD ensures that more power is effectively used, not wasted.
???? Minimizes Need for Oversizing
Systems with high harmonics often need oversized components (like transformers and cables). Reducing harmonics removes the need for these costly design changes.

???? Where Are Low Harmonic VFDs Used?
Low harmonic VFDs are ideal for:
Hospitals and Medical Facilities (sensitive imaging and life-saving equipment)


Data Centers (to avoid server malfunctions)


Manufacturing Plants (especially with large motors or long cable runs)


HVAC Systems in Large Buildings (clean power for chillers and fans)


Water and Wastewater Treatment Plants (where pump and blower reliability is critical)