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what is generator THD?

BISON will take an in-depth look at the concept of THD and its impact on generator performance and electronic equipment to ensure optimal power quality.

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Portable generators, the ubiquitous powerhouses, have become a staple in our lives, providing electricity to homes, businesses, and industries during power outages or in remote locations. However, the quality of power they generate is as critical as the power itself. One key aspect that influences this quality is Total Harmonic Distortion (THD).

In this paper, BISON will take an in-depth look at the concept of THD and its impact on generator performance and electronic equipment to ensure optimal power quality. In addition, BISON will look at ways to reduce the THD of generators to improve their efficiency and lifetime.

So, whether you’re a seasoned electrical engineer, a generator owner, or just someone curious about how your power source works, this article promises to shed light on the somewhat complex subject of THD. Let’s embark on this illuminating journey together!

what is generator thd

what is generator THD?

Total Harmonic Distortion (THD) represents the level of harmonic distortion present in a generator’s power output. It is expressed as the percentage of harmonic distortion in the generator’s voltage or current waveform relative to the fundamental waveform. Harmonics, which are multiples of the fundamental frequency, can lead to power quality issues such as generator overheating, equipment malfunction, and reduced efficiency.

Harmonics are essentially multiple integer frequencies of the fundamental frequency. For instance, if your generator operates at a fundamental frequency of 50Hz, the second harmonic would be 100Hz, the third 150Hz, and so on. These harmonics can distort the original or ‘fundamental’ waveform, reducing the quality of power output.

High THD levels and their effects

Taking THD into account is crucial since it can influence the generator’s performance and efficiency, as well as the power quality of the electricity generated. Elevated THD levels may result in equipment breakdown, diminished power quality, increased power consumption, and even damage to the electrical grid. 

High THD levels can also have numerous negative effects on generators and electrical equipment. Some potential issues include:

Reduced efficiency of generators

High harmonic distortion can cause increased power consumption and heat dissipation, which can decrease the generator’s efficiency. This can lead to higher operating costs and reduced lifetime of the generator.

Erratic AVR function

The AVR helps to maintain a constant voltage level. However, a high THD can cause the AVR to function erratically, leading to unstable voltage levels that can damage connected devices.

Erratic speed fluctuations

Harmonics can cause equipment failure, malfunctions and premature aging. This can lead to costly repairs and replacements, as well as decreased productivity.

Limiting continuous load ratings

Generators with high THD levels might not be able to sustain their rated loads for extended periods. This can limit their usability and lead to premature wear and tear.

Overheating and failure of electrical insulation

High THD can lead to excessive heat buildup, which can cause the insulation on wires and other components to fail. This can lead to short circuits and potential fire hazards.

the generator is connected to the electrical

How to reduce generator THD?

High THD levels can significantly affect the performance and lifespan of sensitive electronic equipment. Devices such as computers, servers, or medical equipment, which rely on clean, undistorted power, can malfunction or even fail when exposed to high levels of harmonic distortion. Moreover, these devices may experience reduced efficiency and increased energy consumption.

There are several methods and devices used to reduce Total Harmonic Distortion (THD) in generators.

Selection of inverter generators

The acceptable THD levels vary depending on the type of generator. For conventional generators, a THD of less than 6% is generally considered acceptable. However, for inverter generators, which are typically used to power sensitive electronic devices, the acceptable THD is much lower, often less than 3%.

Filters and Line Conditioners

These are devices that can be added to a power system to filter out harmonic frequencies, thereby reducing THD. Filters work by blocking or attenuating unwanted frequencies while allowing desired frequencies to pass through. Line conditioners, on the other hand, improve the quality of the power that’s delivered to electrical load equipment by ensuring a constant voltage level and reducing the effects of power surges and noise.

Harmonic Compensators or Neutralizers

These are advanced devices that generate a counteracting harmonic current to cancel out the harmonics in a power system. They effectively neutralize the distortion, leading to a cleaner power output.

Power Factor Correction (PFC) Devices

PFC devices help to improve the power factor of a power system, which can indirectly help to reduce THD. By making the power factor closer to 1, these devices maximize the efficiency of power delivery.

inverter generator connected to the refrigerator

You’ll typically find the Total Harmonic Distortion (THD) detailed in the product’s specification chart or labeled directly on the product.

According to IEEE Standard 519, it’s suggested that devices like computers and programmable controllers should use an AC power source with a maximum of 5% harmonic voltage distortion. Additionally, no single harmonic should exceed 3%.


In conclusion, understanding Total Harmonic Distortion (THD) is crucial for anyone looking to make an informed generator selection. THD measures the deviation of a generator’s output waveform from a perfect sine wave due to the presence of harmonics, and high levels of THD can negatively impact power quality and the performance and lifespan of both the generator and the electronic devices it powers.

Following these guidelines can ensure safe and efficient generator use, protecting your electronic equipment from potential damage caused by high THD levels. It’s not just about selecting a generator; it’s about choosing a power solution that offers reliability, efficiency, and protection for your devices.

BISON inverter generator manufacturers

As a leading manufacturer of inverter generators. One excellent choice is BISON’s range of inverter generators. Known for their low THD output, BISON inverter generators are designed to safely power sensitive electronic equipment, providing clean, stable power that you can rely on.

Don’t gamble with your power needs. Choose wisely, choose BISON. Experience the difference of low THD output with BISON inverter generators today. Your electronic equipment will thank you for it.

about generator THD, people also ask

The limits vary depending on the type of generator and the application, but generally, the THD level should be less than or equal to 5% for industrial and commercial applications and less than or equal to 8% for residential applications.

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