Effects of harmonics on electronic equipment

Power Quality and Its Importance

Power quality refers to the stability and performance of an electrical system. Specialized instruments measure it in three-phase electrical systems by assessing various factors. Addressing power quality issues can help your facility save on energy costs and protect equipment from potential damage.

The first step in evaluating power quality is to gather data from your equipment, infrastructure, and service panel. Key issues resulting from poor power quality include:

• Voltage dips and swells – periods when voltage is lower or higher than expected.
• Harmonics – frequency distortions caused by the power supply or equipment operating in the system.
• Unbalance – variations in voltage or current across the three electrical phases.
• Flicker – disturbances from frequent switching of electrical loads, such as those from arc furnaces or similar processes.

Understanding Harmonics in Electricity

Harmonics are electrical currents or voltages with frequencies that are integer multiples of the fundamental power frequency. In the United States, the fundamental frequency is 60 Hertz (Hz). Thus, the first harmonic is 60 Hz, the second is 120 Hz, the third is 180 Hz, and so on. Harmonics can cause various power quality issues, including:

• Flickering Lights: This is a common symptom of power quality problems. You can often trace flickering back to machinery that experiences rapid fluctuations in load current or voltage.

Large industrial motors make huge noises when start up. Machines with cyclo-converters, like rolling mill drives and mine winders, also produce noise. Additionally, equipment that uses static frequency converters, such as AC motors and electric arc furnaces, can be noisy too.

• Overheated Transformers and Tripped Breakers: These issues may indicate harmonic problems caused by non-linear loads. These loads use current in quick pulses instead of a smooth, sinusoidal way. This creates harmonic currents that can return to other parts of the power system.

Impacts on Power Electronic Equipment

Power electronic devices depend on accurately detecting voltage zero crossings and other critical features of the voltage waveform. Harmonics can disrupt these zero crossing points, as well as the moments when one phase voltage surpasses another. Such disruptions can lead to improper operation of electronic circuits, which rely on precise control signals.

Medical Equipment

The effects of harmonics on medical equipment can be particularly detrimental, posing significant risks to patient safety. To mitigate these risks, many medical devices utilize line-regulated power and incorporate power-quality equipment designed to ensure safe and reliable operation.

Computers and Other Electronic Devices

Devices like programmable controllers require a harmonic voltage distortion factor of no more than 5%, with any single harmonic limited to a maximum of 3% of the fundamental voltage.

When these harmonic distortion thresholds are exceeded, it can lead to equipment failure and potentially serious consequences.

Addressing Excessive Harmonics

When a system experiences excessive harmonics, it is crucial to analyze the specific harmonic issues at play. One effective solution is to purchase harmonic filters and install them as close as possible to the equipment generating the harmonic currents. Selecting the appropriate harmonic filter depends on the specific harmonic order involved.

In some situations, isolating the problematic equipment using an isolation transformer or relocating the non-linear load causing the harmonics to a different switchboard can help mitigate the issue.

Effects of Harmonics

Excessive harmonics can significantly shorten the lifespan of electrical equipment. When motors and drives get damaged from harmonic distortion, they might need to be replaced early. This can lead to a lower return on investment.

Additionally, harmonics can lead to overheating of equipment, which puts stress on cables and diminishes the overall performance of electrical systems.

Reducing Harmonics with Active Harmonic Filter

1. Conduct Harmonic Analysis: Measure Total Harmonic Distortion (THD) to identify specific harmonic issues in your system.
2. Select the Right AHF: Choose a model that matches your power requirements and the identified harmonics.
3. Installation: Install the AHF close to nonlinear loads, following YT Electric’s installation guidelines.
4. Configuration: Set and tune the AHF to optimize its performance based on real-time load conditions.
5. Monitoring & Maintenance: Use monitoring tools to track performance and schedule regular maintenance for optimal operation.
6. Documentation: Keep records of installation and performance to ensure compliance and track effectiveness.

YT Electric is the biggest OEM manufacturer of low-voltage AHF and SVG with more than 15 years' experience. All products hold certifications for ISO9001, CE, and CQC standards, and type test reports support them.

For more information on how our AHFs can help manage harmonics and improve power quality:

Contact us at sales@ytelect.com