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Harmonic frequencies in electrical systems

What are harmonics

Harmonics are distorted electrical waveforms that introduce inefficiencies into your electrical system. They produce wasteful heat and can cause plant issues and fees from your local power company.

Harmonic frequencies flow into the electrical system as a result of nonlinear electronic switching devices, such as variable frequency drives (VFDs), computer power supplies and energy-efficient lighting. Similarly, companies with heavy motor, VFD and lighting loads need to be aware of the problems that harmonics can cause. 

These problems include:

  • Increased electrical usage
  • Increased wear and tear on motors/equipment
  • Higher maintenance costs
  • Power quality problems upstream and downstream
  • Utility penalties for introducing problems to the power grid

The charts shown below illustrate motor and transformer efficiency decreases due to system harmonic frequencies.

Induction Motor Efficiency at constant load
Transformer efficiency - 75kVA example

Educational overview on harmonics

The Eaton Power Systems Experience Center (PSEC) gives an educational overview on harmonics that covers IEEE 519, variable frequency drives (VFDs), VSDs and power quality issues that affect your electrical system.

Harmonic frequencies alter an electrical wave, distorting the power

Perfect wave
Take a perfect wave with a fundamental frequency of 60 Hz, which is close to what is supplied by the power company.
Second wave
Add a second wave that is five times the fundamental frequency - 300 Hz (typical of frequency added to the line by a fluorescent light).
Resulting supply wave
Combine the two waves. The result is a 60 Hz supply rich in fifth harmonics.

How do harmonics occur and who should be concerned

Harmonics are generated by electronic equipment with nonlinear loads. Nonlinear loads are most often created by modern electrical equipment, such as variable frequency drives, fluorescent lights, computers, uninterrupted power supplies (UPS) and other items.

Harmonics impose negative consequences on power systems. The concern for the power system and results of the harmonics impact specific roles within an organization, which goes well beyond the typical system maintenance staff.

Specific industries can greatly benefit from low harmonic drive solutions. The largest served segments including:

  •  Water and wastewater
  •  Elevators and escalators
  •  Commercial HVAC
  • Conveyors

Find out more specifically about how harmonics are created and which roles within an organization should be attuned to their effects.

VFD with harmonic distortion graphic
Discover common causes of harmonic distortion in the power system.

What effects do harmonics have on a power system?

The consequences of harmonic distortion in a power system cause both financial and technical issues. From system components running too hot and suffering additional wear, to productivity losses to downtime, harmonics wreak havoc on a power system and your financial bottom line.

Take a look at some of the effects of harmonics in the power system that can occur.

Effects of harmonics icons
Learn more about the financial and technical issues that result from harmonics

How to reduce harmonics in power systems

There are multiple methods for reducing harmonic voltage and current distortion from nonlinear distribution loads such as VFDs. 

We compare the following techniques:

  • No method implemented
  • DC choke
  • Line reactor
  • 12-pulse converters
  • 12-pulse distribution
  • Harmonic trap filters
  • Broadband filters
  • Clean power, 18-pulse converters
  • Active filters

Take a look at 9 common harmonic reduction methods along with the advantages and disadvantages of each.

Discover and compare 9 different methods of harmonics reduction

Harmonics mitigation - take action today

Low-harmonics VFDs

Eaton offers a number of low-harmonics VFDs. Harmonics can be diminished by applying drives from the Eaton clean power drives family: EGF and CFX passive filtered drives, EGF and CPX 18-pulse drives, and RGX regenerative drives.

At a glance compare our low harmonics drives. The features and benefits are listed for each. This includes communication protocols, horsepower range, input voltage, footprint size and more. Standards and certifications are listed for each drive.

Eaton low harmonics VFDs
Compare low harmonics drives to determine which would best fit your situation

Harmonics calculator

Download our easy-to-use harmonics calculator that will allow you to model your electrical system motor loads and controllers to check compliance with IEEE-519 2014.

Our free harmonics calculator, unlike many others you may find online, is actually downloadable software. You will be able to make calculations from your computer rather than returning to a website each time you need to make a new calculation.

Download our harmonics calculator

   Harmonics FAQs

Do all loads create harmonics?

No. Linear loads, like those produced by a light bulb or a standard driven motor do not produce harmonics. The load they draw looks similar to the voltage.

Nonlinear loads, like those produced by fluorescent lights and VFDs draw current that does not look similar to the voltage. These produce harmonics.

How can I reduce harmonics in my system?

There are several options that can be used to reduce harmonics in a system. These include:

  • Inductive reactors
  • 12-pulse converters
  • Passive filters
  • Active harmonics
  • Active front end drives
  • 18-pulse converters

What is the distribution by horsepower of low harmonic VFDs sold?

Total low-harmonic VFDs sales by horsepower.

  • 41% - greater than 335 hp
  • 32% - less than 100 hp
  • 27% - between 100 hp and 335 hp