Everything You Need to Know About The Basics of Harmonics

Your Guide to Understanding Harmonics


Harmonics drastically affect your operational costs, so it is critical to gain a basic understanding of the concept. At Alpha Power Solutions, we have had many requests about the topic, to keep companies functioning optimally.

Addressing how harmonics work and affect the quality of your power when running your equipment helps you to work towards the peak performance of your operations.

The underlying workings of harmonics can be a challenge to understand when you haven’t done an advanced electrical study.

In a nutshell, it is a form of electrical “pollution” that causes substantial problems for your operational equipment. This problem makes it essential for technicians and managers alike to understand how to tackle it.

We look at what harmonics are (technical explanation), what steps you can take to reduce the problem, and how to mitigate your company risk.

What are Harmonics?

In physics, they give a “simple” definition of harmonics – as a component frequency of an oscillation or wave. What, we might hear, you ask? More in-depth descriptions extend to “a signal or wave whose frequency is an integral (whole number) multiple of the frequency of some reference wave or signal.”

Let’s make this easier by providing some details of the various components of harmonics. In effect there are 2 types of frequencies;

  1. Fundamental frequency
  • is produced by the oscillation of the whole object
  • and leads to a fundamental or periodic wav
  1. Harmonic frequency
  • is a multiple of the frequency of the fundamental wave

When you have a combination of the fundamental wave as well as one or more harmonic waves, we call this a “distorted periodic wave.”

Defining Harmonics from a local perspective

In South Africa, the fundamental frequency of electricity is 50Hz. You can calculate your harmonics via multiples of the base frequency;

  • 3rd harmonic frequency (3 times the fundamental frequency) is 150Hz
  • 5th harmonic frequency (5 times the fundamental frequency) is 250Hz
  • 7th harmonic frequency (7 times the fundamental frequency) is 350Hz

Important to understand is that a fundamental wave typically looks like a sine wave. Below you will see how, when you introduce a harmonic wave together with a fundamental wave, that the different shapes result in a distorted wave.

Look at a “period” as one peak and one trough. The 5th harmonic, of the fundamental wave, would be;

  • 2 ½ waves in a single peak
  • 2 ½ waves in a single trough

The first diagram shows that the fundamental wave is made up of 5 waves in one period. The second diagram depicts a harmonic distortion. This distortion is the;

  • the degree in which a waveform deviates from its pure sinusoidal values
  • this is results from the summation of all the harmonic elements

So, an ideal sine wave has zero harmonic components.

Fundamental 50 Hz wave and 5th Harmonic wave                                                Resulting distorted wave

By having these distortions, there are added peaks and troughs in the system. These are what cause your equipment to get electrical surges. Ultimately this is what damages the internal workings of your electrical equipment, costing you time and money.

Understanding the cause and effects of harmonics

Harmonic distortions do not occur randomly. Several sources in an electrical installation generate a significant amount of harmonic current. These sources are typically non-linear loads such as;

  • large Variable Speed Drives
  • DC drives and rectifying banks

When current and voltage harmonic levels are within acceptable levels, they are not harmful. When they elevate, they can have destructive consequences, including;

  • Increased current in the system
  • Increased peak-to-peak voltage
  • Overheating of electrical equipment
  • Shorter lifespan of electrical equipment
  • Incorrect operation of protection devices
  • Interference with communication lines
  • Incorrect reading of meters

All these issues can cause your electrical equipment not to operate as smoothly as you had hoped. Effectively this causes increased electrical costs and decreased equipment up-time, and nobody can afford to run their company in this way.

How do you mitigate harmonics and the adverse effects?

There are several ways to reduce the harmonic levels in your electrical installations. We address the 3 methods below.

  1. Retrofitting line reactors on large VSD’s
  2. Install active or passive harmonic filters
  3. Installing harmonic blocking reactors

The first method is to limit the amount of harmonic current introduced by the VSD’s into the distribution system. The second option of filters reduces excessive harmonic levels in electrical installations.

For the third method of incorporating harmonic blocking reactors in power factor correction equipment, the capacitors in a PFC system do not generate harmonics, but they amplify existing harmonics present in an electrical installation.

By installing harmonic blocking reactors in series, with the capacitors in a PFC system, you prevent the amplification of the harmonic levels.

In systems where acceptable harmonic distortion levels exist, the introduction of standard PFC equipment without harmonic blocking reactors can result in the harmonic levels elevating to unacceptable levels.

Let Alpha Power Solutions ensure your electrical equipment operates optimally

By mitigating the adverse side effects caused by elevated harmonic levels, you improve the availability and life expectancy of your electrical equipment.

Not sure on your levels, and what is or is not acceptable?

Alpha Power Solutions can assist you with the analysis of the harmonics present in your factory. This analysis allows for a tailor-made solution that is designed to increase your efficiencies. We also offer a 360-degree PFC offering, supplying and installing the recommended equipment, which reduces the harmonics to acceptable levels.

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