Total Harmonic Distortion

What Is Generator THD?

The THD is the total harmonic distortion, which is the cumulative distortion in the current and voltage curves. It is a complex concept, so we need technical knowledge of physics and math to fully comprehend it. Our aim is to keep it as simple as possible, so that any layman can understand it without any technical background. 

Before we move on, let us understand the terms involving the explanation of total harmonic distortion, which are alternating current (AC), direct current (DC), and sinusoidal wave. 

Sine Wave:

Pure Sine Wave

It is a graphical representation of a sine function that describes a periodic oscillation of a wave about a mean position. Two cycles exist, one above the horizontal line is called the positive cycle, and one below is called the negative cycle. Sometimes it is referred to as the sine curve. 

There are many phenomena that occur as sine waves, such as radio signals, voltage waves, current waves, light, etc.

Alternating Current (AC)

Alternating Current

A current that alternates its direction periodically is known as an alternating current. It grows from zero to maximum, reverts to zero, and grows to maximum in the negative direction, reverts to zero, and continues periodically indefinitely. This is similar to the sine curve. 

Direct Current (DC)

Direct Current

This type of current has only one cycle, it starts at zero and grows to maximum, then decreases to zero, and then again grows to maximum and zero in the same direction. The process repeats indefinitely. 

What is THD?

A voltage or current wave that does not resemble the sine wave and is distorted from its original shape is known as total harmonic distortion in a power system, whether it is coming from an external power source or from you driving power using a portable generator. 

What Is Generator THD?

When there is distortion in the current wave, it is total harmonic distortion. Whenever we drive power from a generator, if the generator is producing a distorted current wave, it is called the generator THD. 

Due to power on/off of different equipment such as ac, fridge, iron, dryer, and generator alternators, the power load at home continuously changes, making it very difficult to maintain a pure sine curve. 

There are two main types of generators in the market: conventional generators and inverter-based technology generators. 

Conventional Generator and THD

Due to uneven loads and alternators, these generators have high levels of THD and sometimes reach 25%, which is not safe for electrical equipment. They are not also recommended for sensitive electronics. 

Inverter Generator and THD

In these generators, AC is converted to DC and then back to AC using a rectifier. Therefore, the output AC is very clean and sinusoidal. Their THD is less than 3%, so they can be used with sensitive equipment such as laptops, tablets, cpap machines, phones, etc. 

What Is The Acceptable Range of THD?

THD should not exceed 5%, above that your equipment’s lifespan may be shortened, and sensitive electronics may be damaged as a result. 

Effects Of High THD 

The high level of thd may result in a rise in temperature, which ultimately reduces the life of equipment. A study found that every 10 degrees increase in temperature could cut equipment life in half. 

A high peak voltage is caused by harmonic distortion, which puts a great deal of stress on the motor and insulation, ultimately resulting in insulation failure.

If exposed to distorted current, sensitive equipment including computers, tablets, cpap machines, and mobile phones can be damaged. 

Benefits Of Low THD

A power system’s total harmonic distortion is an important factor. It should be kept as low as possible. Low THD means higher power factor, lower peak current, which results in maximum power efficiency. 

A low THD in current is similar to a pure sine wave. This increases equipment life. They provide maximum efficiency. You can use sensitive equipment with electricity that has low THD.

Final Thought

Harmonic distortion is an important term in the power system. A low THD results in better efficiency and maximum equipment life, whereas a high THD results in low efficiency and equipment failure. 

[1] Consequences-of-high-harmonic-distortion-levels
[2] Total Harmonic Distortion in Power systems
[3] Total Harmonic Distortion
[4] Total Harmonic Distortion and Electrical

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