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What is harmonic distortion and why does it matter?

Why harmonics matter

Harmonic distortion is also known as harmonics. Harmonics are distortions in the mains power network which can lead to poor power quality, an unreliable power network, and eventually to equipment damage.

Discover harmonics
For engineers and planners

Early planning and mitigation of harmonics helps you to

  • Prevent downtime from motor and transformer overheating, and
  • Downsize transformers and backup generators
  • Reduce unplanned system failure
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For consultants
For consultants

Specify harmonic mitigation correctly, for more cost-efficient projects in both the CAPEX and OPEX phases:

  • Reduce operating costs overall
  • Meet environmental targets
  • Optimize production facilities
Meet your targets
For executives

Manage risk of electrical inefficiencies due to unchecked harmonic distortion:

  • Control energy costs and capital expenses
  • Comply more economically with regulations
  • Enhance uptime and profits
Manage hidden risk

Why does harmonic distortion matter?

Did you know that network operators work hard daily, to bring us high-quality power in the electrical network? It’s an ongoing task to ensure that the power delivered to our homes and factories is clean alternating current, free of harmonic distortion.

When drawing power from the network, the network supply can become distorted by the loads that are connected to it. This power distortion includes harmonic components.

For factories and other industries, harmonics and other power distortions cause problems that cost money, such as:

  • Damage to critical equipment for example by overheating, which can reduce equipment lifespan and lead to malfunction or failure
  • Higher energy bills due to poor efficiency and charges for the additional distortion, resulting in lower profitability
  • Difficulty in meeting targets for productivity and climate
  • Unreliable power supply due to poor power quality in the network in general
Play the video to learn how to mitigate harmonics - to reduce cost and risk.

Consequences of harmonic distortion

Malfunction: How does harmonic distortion cause damage to critical equipment?

Harmonic distortion in electrical systems damages equipment by causing overheating, voltage stress, and energy losses, which strain components and reduce their lifespan. The effects of more harmonic distortion are far-reaching, as they affect every piece of electrical equipment connected to the same system.

Excessive harmonic distortion can cause cables and motors to overheat. Motors, switchgear, fuses, cables, and sensitive measuring equipment are all impacted. Distortion with harmonic content can even interfere with critical telemetry and communication devices like Wi-Fi systems.

This can lead to premature equipment failure, such as blown fuses, tripped circuit breakers, or overheated motors, potentially affecting the entire industrial plant if no corrective measures, like harmonic filters or power quality improvements, are implemented.

The image shows the influence of harmonic distortion generators in overheating of electric motors.

Excessive harmonic distortion can cause cables to overheat.
Efficiency: How does harmonic distortion lead to higher power bills?

Harmonic distortion increases power bills by increasing system losses and reducing overall system efficiency.

This wasted energy is a major operating cost issue for industrial users.

To reduce the total bill whilst still getting the same amount of useful power, we need to reduce harmonic distortion.

Electricity bills are made up of active and reactive power. Only the active power is usable, but we pay for both components. The extra cost can impact profitability.

Productivity: How does harmonic distortion influence our productivity and climate efforts?

Power distortions, including harmonics, are more than just annoying. They can stop your processes, causing downtime and interruptions to your production lines. They also affect the CAPEX when purchasing equipment and fuels to operate your plant, which has a major impact on operating cost targets.

Harmonic distortion and distortion in general also impact greenhouse gas (GHG) emission targets across all Scopes (Scope 1, 2 and 3 emissions). Distortion of the power supply results in these undesirable outcomes:

  • Equipment is oversized in order to withstand damage
  • Equipment operates inefficiently
  • Distortion prevents energy efficiency initiatives from going ahead

The good news is that harmonic distortion, including higher frequency harmonics and lower order harmonics, can be mitigated. By putting measures in place to keep voltage distortion at low levels, you can:

  • Increase transformer loading capability. This means you can reduce the size of transformers and generators required
  • Prolong equipment life
  • Increase equipment efficiency, for lower losses
  • Reduce risk of power trips and production stoppages
Power quality: How does harmonic distortion cause general unreliability in networks?

Harmonics cause unreliability in networks by distorting the electrical waveforms, which can negatively affect the performance of sensitive equipment and systems. As more non-linear electrical devices are added to a system, the system becomes more vulnerable to these distortions.

Therefore, it is important to consider harmonics and how to mitigate them, to build a resilient system that does not fail.

Harmonics FAQ

How do AC drives affect harmonics?

AC drives bring a multitude of benefits to your system, especially in reduced energy consumption. At the same time, they generate more harmonics - and can also mitigate these harmonics produced. The reason to use AC drives is that their benefits far outweigh the drawbacks of harmonics produced. Discover the benefits in this video.

AC drives: The best way to reduce energy consumption

AC drives, also known as variable speed drives (VSDs) or variable frequency drives (VFDs), offer the best way to de-carbonize your operation and meet your carbon neutrality targets. These drives regulate electric motors to reduce energy consumption dramatically. They also bring controllability, repeatability, and resilience to industrial processes.

Drives are an integral part of the modern industrial landscape, bringing enormous benefits:

  • Process quality levels rely upon regulation by drives
  • Adaptable process line throughput is only achievable using drives
  • Variable demands on water supplies or HVACR ventilation can only be managed using drives
  • Modern industrial and commercial facilities can only operate efficiently by controlling electric motors properly, which requires use of a drive

New-build projects and upgrades to existing systems

New installations can reduce energy consumption by equipping each application with AC drive control. Upgrading existing direct-on-line (DOL) or fixed speed installations to drives is the best way to achieve greenhouse gas (GHG) reduction goals 1]. Upgrading to high-efficiency motors helps even more.

1] OMDIA COP26 global report: If all fans and pumps globally were equipped with VSDs, the savings would equal the entire power generation capacity of the EU. By employing drives, GHG emissions can reduce by 40% by the year 2040.

There are many ways to reduce total harmonic distortion. Danfoss helps you find the best

There is a lot of money to save, and many other benefits. to be won, by mitigating harmonics properly. However, there is no single solution for all scenarios. It’s a matter of selecting the best method for each individual installation. In some cases, you can achieve compliance with no mitigation at all, so don't buy what you don’t need!

Consider dealing with a manufacturer that understands the challenges and can offer you the best advice for your exact system and circumstances. Danfoss offers the widest range of solutions to mitigate harmonic distortion, in high or low power range, compatible with any motor technology, to suit any situation. We help you to find the most efficient and economical solution.

Modern drives (and filters) from Danfoss can mitigate harmonics and manage the harder issues like supra harmonics and common mode. There is no single solution for all scenarios. Have questions? We can help.

The full range of harmonic mitigation solutions includes:

  • Built-in chokes in the AC drive, integrated in the standalone drive or enclosed drive cabinet
  • Passive solutions, including 12-pulse and 18-pulse drives, passive filters, and low harmonic drives
  • Active solutions, including active filters and ultra-low harmonic drives

For planners: To find the optimal mitigation solution try our digital tool,  MyDrive® Harmonics.

Harmonics FAQ

Are you familiar with harmonics?

To learn more about harmonic distortion and how to mitigate them, check the FAQ topics below, and read our blog.

Explore the blog
What is harmonic distortion?

Harmonics are not visible, but their effects are. Harmonic distortions are repetitive and continuous deformations of the clean voltage or current waveforms.

Using Fourier analysis, a technique developed by the French mathematician, we can visualize the magnitude of harmonics present in the system.

Fourier showed that any distorted waveform is just a set of individual sine waves of different frequencies and amplitudes added together. The distorted waveform is made up of a sinusoidal fundamental curve, plus harmonics.

It is these individual higher order sine waves that are known as harmonics. Usually, we refer to power distortions in the frequency range under 2 kHz as “harmonic distortion”.

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Where do harmonics come from?

Harmonic distortion of the waveform originates from non-linear loads connected to the power supply. All loads that draw non-sinusoidal current are referred to as non-linear loads. The biggest contributors to harmonics are:

  • Switch mode power supplies
  • Florescent and LED lighting equipment
  • Uninterruptable power supplies (UPS)
  • Frequency converters, also known as variable speed drives (VSD), variable frequency drives (VFD), AC drives or just drives
How to mitigate harmonics

To reduce damage to equipment, regulations limit harmonics to low levels in power supply networks. Mitigation is not always necessary, but when required, harmonic mitigation devices can reduce harmonics to comply with these regulations. For successful harmonic mitigation there are many methods to choose between, including the use of harmonic filters, active front-end (AFE) drives, and more.

Contact one of our application experts for advice.

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Explore more about harmonic mitigation

Harmonic mitigation - Reduce risk and optimize operating costs

Harmonic mitigation reduces unwanted frequencies in electrical systems, preventing equipment damage, and improving power quality and efficiency.

Is harmonic distortion costing you money and downtime?

Harmonic distortions can lead to breakdowns and damage in electrical systems. Reduce risk and minimize downtime with filters and low harmonic drives, LHD and ULH, from Danfoss.

Aerial view of a wastewater plant, with blue lights indicating condition monitoring sensors

Danfoss Drives: World-leading drive manufacturer

Danfoss is the global power converter and VFD manufacturer delivering efficient optimization of any electric motor or system, since  1968. We are committed to improving productivity, efficiency and emissions for a wide range of industries, OEMs and system integrators, making Danfoss Drives a reliable manufacturer of your drives.

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