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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

Want to better understand how harmonics impacts your facility?

We recently hosted a live Ask the Experts event that looked in depth into harmonics.  We will explore what causes harmonic distortion, the impact, various mitigation methods and so much more.

Watch a recording of the event

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

Harmonic solutions explained

Our new white paper provides technical recommendations for reducing harmonic distortion, improving system capacity and improving system reliability while evaluating installed costs.

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), variable speed drives (VSDs) and power quality issues that affect your electrical system.

Who should be concerned about harmonic distortion?



There are many business implications to managing harmonic distortion. In today’s competitive business environment, better awareness of electrical inefficiencies result in:

  • Controlled capital expenses
  • IEEE 519 compliance
  • Increased uptime and profits
  • Added value to facilities
  • Reduced energy expenses

Maintenance and facility engineers

Taking a proactive approach to harmonic reduction helps to protect sensitive electronic equipment and reduce downtime due to motor and transformer heating.

It also eliminates the problems associated with sizing and applying backup generators on systems with high harmonics caused by drive loads.


Business owners and stakeholders

Taking steps to curb harmonics can improve return on investment and boost the intrinsic value of the facility or the enterprise.

Managing the electrical infrastructure will help to protect electrical assets and contribute to a "greener" environment by reducing utility CO2 emissions.

   Harmonics FAQs

How do you calculate total harmonic distortion (THD) and total demand distortion (TDD)?

Learn who should care about harmonics including electrical designers, consultants, contractors, electricians, utility personnel, customers, owners and more.

 View all Harmonics FAQ videos