The Basics of Passive Harmonic Filters

February 15, 2021


Passive harmonic filters are commonly used on the input side of motor drive systems. Their purpose is to mitigate the amount of harmonic distortion produced by variable frequency drives (VFDs). If this harmonic distortion is left unaddressed it can further distort the utility grid or cause damage to nearby equipment. The IEEE-519 standard sets a voltage and current distortion limit of 5% for electrical systems. In certain regions, such as the Permian Basin, grid voltage distortion is becoming an increasingly larger problem. Grid voltage distortion levels have gotten so bad in these areas that utility providers have begun measuring the amount of distortion coming from well sites. If the measured harmonic levels do not meet the utility companies standard, they will issue a fine or cut off power to the site.

The Benefits of Passive Harmonic Filters:

Take the harm out of harmonics – Installing a passive harmonic filter between the utility gird and the VFD, protects the grid from drive produced harmonic distortion. The VFD and passive harmonic filter combination reduce overall input harmonic distortion, helping you maintain IEEE-519 compliance. Operating a motor drive system without a harmonic filter can cause several problems:

  • If you are generator powered, a high level of reflected harmonics can cause unwanted nuisance tripping.
  • Elevated levels of harmonic distortion force you to derate the size of your generator in order to compensate. Generator derates can be as high as 3 times the desired power rating.
  • The motor drive system could be sending significant harmonic distortion back to the utility grid, effecting IEEE-519 compliance.
  • Harmonic distortion can effect other equipment connected to the same grid system.

CTM GridHawk filters solve all of these problems while reducing capitol investment (CAPEX), operating cost (OPEX), and increasing over all system efficiency. In all, CTM has filters designed for max current loads between 80 and 950 amps, providing a wide selection of products and price points. Not all passive harmonic filters are equal. Learn more about what sets CTM Gridhawk filters apart from all other harmonic mitigation solutions.

For more information on passive harmonic filter basics, contact CTM today.

More Resources

CTM Filters Lower PM Motor Drive Investment

Lower the capital investment (CAPEX) of your motor drive system. Avoid costly derates, without sacrificing performance. A better solution exists today.   CTM HighSine™ & FlexSine® Filters  Terminology: VFD (THD OUT): The total harmonic distortion...

High Frequency Filtering For High Speed Motors

High Frequency Motor Applications Require Extra Filtering   High frequency motor applications lead to higher harmonic distortion for the entire motor drive system. To account for this one can either reduce the harmonics by derating the VFD, increasing the drive...

GridHawk® Series Advantages

GridHawk Passive Harmonic Filters   CTM’s GridHawk® series passive harmonic filters boast several key advantages over market standard harmonic filters. These advantages include: High Grid Voltage Survivability GridHawk® filters are unique in that they are built...

Film Capacitors vs. Electrolytic Capacitors

Film Capacitor Advantages   CTM Magnetics utilizes high-reliability poly-film capacitors. Compared to the electrolytic capacitors used in our competitors’ filters, CTM's film capacitor advantages include higher temperature ratings, higher surge voltage ratings,...

Sealed Contactors Protect Outdoor Harmonic Filters

Sealed Contactors Protect Outdoor Harmonic Filters   Many harmonic filters use NEMA 3R outdoor cabinets in blowing dust or high humidity environments. A harmonic filter awaiting installation in the field for 30 days can collect enough dust on the contactor to...

CTM Sine Wave Filters Don’t Create Common Mode Noise

Common Mode Noise Protection   Conventional sine wave filters introduce a substantial amount of common mode noise. Common-mode (bearing) current can have disastrous effects on induction motors, leading to electric fluting and premature bearing failure. As a...

Small. Quiet. Efficient. Reliable

Stop trying to make silicon steel "work"