This engineering guide from Circuit Energy explains the fundamental nature of harmonics in modern electrical networks. As low-voltage networks increasingly power non-linear loads, understanding these frequency distortions is essential for preventing equipment failure and maintaining power quality

What are Harmonics?

Harmonics are electrical signals with frequencies that are integral multiples of the basic supply frequency. For a standard 60 Hz supply, the 5th harmonic vibrates at 300 Hz. Every periodic signal is the sum of its fundamental component and various harmonics

Common Sources of Distortion

Electrical loads are categorized into two types based on how they draw current:

• Linear Loads: These draw sinusoidal current and include ohmic resistances like light bulbs and heaters, as well as three-phase motors without drives
• Non-Linear Loads (Harmonic Generators): These distort the original supply voltage and include UPS systems, computers, rectifiers, and variable-speed induction motor

Why Different Harmonics Matter

• These occur due to asymmetrical loads or single-phase sources and can cause major problems as currents in the neutral conductor are cumulative
• Generated by three-phase sources or pulse converters, these harmonics are capable of being transmitted via the transformer

• These typically only occur due to sudden load variations or converter fault

Harmonics can lead to cumulative neutral current issues and transformer overheating. Download the full technical document to learn how to calculate Total Harmonic Distortion (THD) and protect your facility from hidden defects