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Test & Measurement

Tip of the Week: Power Quality, Part 3

Oct. 30, 2017

Excess harmonics may cause all sorts of problems.

Excess harmonics will cause all sorts of problems. But where do these come from?

The greatest contributors to harmonics are lighting circuits with electronic controls. Lighting accounts for about half of all electrical power consumption.

And more than half of that power is controlled by a type of switching mode switching mode power supply (SMPS). So about 30% or more of all electrical power contains harmonics.

The next largest contributors are computers. Any single-phase device that contains an SMPS will cause high levels of 3rd harmonics. The 3rd harmonic causes the greatest amount of distortion.

With industrial settings, lights and computers may account for 70% of the total load. Non-linear 3-phase drives (AC or DC) are usually less than 20% of the total load. Line conditioning equipment causes distortion on the AC line while protecting computers.

The third largest contributors are motors. Motors are increasingly controlled by variable speed drives, which contribute to harmonics except when a given drive is harmonics-corrected. Many are also power factor corrected.

About the Author

Mark Lamendola

Mark is an expert in maintenance management, having racked up an impressive track record during his time working in the field. He also has extensive knowledge of, and practical expertise with, the National Electrical Code (NEC). Through his consulting business, he provides articles and training materials on electrical topics, specializing in making difficult subjects easy to understand and focusing on the practical aspects of electrical work.

Prior to starting his own business, Mark served as the Technical Editor on EC&M for six years, worked three years in nuclear maintenance, six years as a contract project engineer/project manager, three years as a systems engineer, and three years in plant maintenance management.

Mark earned an AAS degree from Rock Valley College, a BSEET from Columbia Pacific University, and an MBA from Lake Erie College. He’s also completed several related certifications over the years and even was formerly licensed as a Master Electrician. He is a Senior Member of the IEEE and past Chairman of the Kansas City Chapters of both the IEEE and the IEEE Computer Society. Mark also served as the program director for, a board member of, and webmaster of, the Midwest Chapter of the 7x24 Exchange. He has also held memberships with the following organizations: NETA, NFPA, International Association of Webmasters, and Institute of Certified Professional Managers.