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Harmonics are the result of nonlinear loads that convert AC line voltage to DC. Harmonics flow into the electrical system because of nonlinear electronic switching devices, such as variable frequency drives (VFDs), computer power supplies and energy-efficient lighting.
The general categories of harmonic producing loads (also called nonlinear loads) are:
Today, the most prevalent and growing harmonic sources are:
| Source | Typical Harmonics* |
| 6-pulse drive/rectifier | 5, 7, 11, 13, 17, 19… |
| 12-pulse drive/rectifier | 11, 13, 23, 25… |
| 18-pulse drive | 17, 19, 35, 37… |
| 24-pulse drive | 23, 25, 47, 49… |
| EC motor | 5, 7, 11, 13, 17, 19… |
| Switch-mode power supply | 3, 5, 7, 9, 11, 13… |
| Fluorescent/LED lights | 3, 5, 7, 9, 11, 13… |
| Arcing devices | 2, 3, 4, 5, 7… |
| Transformer energization | 2, 3, 4 |
For VFDs, H = NP +/- 1 * Harmonic magnitude decreases as harmonic order increases |
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Harmonics in power systems result in increased costs and downtime. Get help from Eaton.
Harmonic sources FAQsLearn and understand if your project will have harmonics issues and which harmonic solution to select.
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