A Dive into Harmonics and Why They Matter

Plain and simple, harmonics are frequencies produced by a standing wave pattern. Harmonics, as far as we are concerned, are multiples of the fundamental frequency. The fundamental frequency is the lowest frequency produced by an object or machine and also signifies the first harmonic. The average fundamental frequency in the United States is 60Hz, and in most other countries, 50Hz. Technically, harmonics go on forever since they are just multiples of the fundamental frequency. However, most electrical issues can only be attributed to distortion in the first 15 harmonics. PowerSight PS2500 and PS3550 analyzers measure up to the 50^th harmonic, and the PS4550 and PS5000 Analyzers measure up to the 65th harmonic.

 

Due to the symmetry of the wave form, the even-numbered harmonics are not displayed. They are simply negative reflections of the positive (odd-numbered) harmonics, so we consider them insignificant. Consequently, only odd-numbered harmonics are shown in power analysis, as it is inferred that even harmonics are the symmetrical inverse.

 

To understand the importance of harmonics, one must be familiar with total harmonic distortion (THD). THD is a measurement of how distorted a wave form is, percentage-wise. High THD is bad news and can result in safety hazards if not addressed. Fortunately, not every kind of equipment is overly sensitive to harmonics. An example of something that may have high THD is energy-efficient lighting, so those powerful bulbs don’t come without risk!

 

Harmonics are a higher-level measurement and does not need to be measured in every power analysis scenario. Nonetheless, we equip our meters with a wide range of capabilities in order to detect almost all power events. High harmonics create more temperature for the same current. High harmonics paired with high THD can be a safety hazard, with the threat of fires and other heat-related dangers. If huge transformers and conductors overheat, their useful life could be cut short due to premature breakdown induced by high temperatures.

 

Generally, the goal is to keep THD for voltage under 5%. The third and fifth harmonics are usual suspects for distortion and big problems. A simple solution may be to install a filter that rids of strong harmonics.

 

Whatever the case may be, PowerSight analyzers can provide all the data necessary to fix an issue with frequency and overheating. Our PS3550, PS4550, and PS5000 all measure harmonics and THD, and the PowerSight Manager – Advanced Software can display these in graphical form or in a data table.