Adjust the harmonic sliders or pick a preset to explore how harmonics distort a clean sine wave.
The harmonic spectrum shows the magnitude of each frequency component relative to the fundamental.
In a balanced 3-phase system, most harmonics cancel in the neutral. Triplen harmonics (3rd, 9th, etc.) do not cancel. They sum as RMS: Ineutral = 3 × √(Σ Itriplen²).
Assumption: this formula applies to balanced phases carrying identical harmonic spectra. Any unbalance puts all orders — including the fundamental — into the neutral, and 5th/7th cancellation also relies on that balance.
Toggle three-phase mode and add triplen harmonics to see the effect.
Harmonics cause additional eddy-current and hysteresis losses in transformer cores and windings. K-rated transformers are designed to withstand the thermal effects of harmonic currents (they do not filter harmonics).
Scenario Lab
Click a scenario to load its harmonic profile, then explore the effects across all views.
Select a scenario above to see its analysis.
Adjust harmonic sliders to see recommendations.
Equipment sizing guidance will appear here.
What Are Harmonics?
Harmonics are integer multiples of a fundamental frequency. In a 60 Hz system, the 3rd harmonic is 180 Hz, the 5th is 300 Hz, and so on. A perfectly clean power system has only the fundamental—a pure sine wave. Real loads add harmonics to the mix.
Fundamental vs. Harmonic Frequencies
The fundamental is the intended frequency—50 or 60 Hz depending on your grid. Every harmonic rides on top of it. The 5th harmonic at 300 Hz completes five full cycles for every one cycle of the fundamental.
Waveform Distortion & THD
Total Harmonic Distortion (THD) quantifies how much a waveform deviates from a pure sine. It's the ratio of all harmonic content to the fundamental, expressed as a percentage. This tool computes THD from selected orders 3–13 only. A full-spectrum meter would include all measurable orders.
Nonlinear Loads
Linear loads (resistors, incandescent bulbs) draw current proportional to voltage—no harmonics added. Nonlinear loads (VFDs, rectifiers, LED drivers, switching power supplies) draw current in pulses or chunks, creating harmonic frequencies.
Common harmonic producers: variable-frequency drives, UPS systems, computers, LED drivers, arc furnaces, welders.
Triplen Harmonics & Neutral Danger
Triplen harmonics are the 3rd, 9th, 15th, etc.—odd multiples of three. In a balanced three-phase system, most harmonics cancel in the neutral conductor. Triplens don't cancel; they sum as RMS. The neutral current from triplens is 3 × √(Σ Itriplen²), not a simple arithmetic sum. This assumes balanced phases with identical harmonic spectra—unbalance adds every order, fundamental included, to the neutral.
Transformer Heating & K-Factor
Harmonics cause extra heating in transformer windings and cores. Eddy-current losses increase roughly with the square of frequency, meaning a 5th harmonic causes ~25× the eddy-current loss per unit current of the fundamental. K-rated transformers are designed to withstand the thermal effects of harmonic currents—they do not filter or remove harmonics.
The Harmonic Heating Index (HHI) = 1 + Σ(h² × rh²). K-Factor = loadPU² × HHI. Standard K ratings: 1, 4, 9, 13, 20, 30, 40, 50.
Power Quality Impact
Distorted waveforms can cause: nuisance tripping of breakers, overheating of conductors and equipment, interference with sensitive electronics, resonance with power-factor correction capacitors, and increased energy losses throughout the distribution system.
Why This Matters
Modern buildings are packed with nonlinear loads. Data centers, LED lighting retrofits, and VFD-controlled HVAC all contribute harmonics. Understanding harmonics is no longer optional for electrical professionals—it's fundamental to designing reliable systems.
Common Mistakes
- Assuming the neutral is always low-current in three-phase systems
- Sizing transformers only for kVA without considering harmonic content
- Ignoring THD until equipment starts failing
- Confusing power factor correction with harmonic filtering
- Thinking K-rated transformers filter harmonics (they only tolerate them)
What to Notice
- Watch how the waveform flattens or sharpens as you add harmonics
- See how the 3rd harmonic alone creates a distinctly “chunky” waveform
- Notice that THD rises quickly once several harmonics are present
- Observe how triplen harmonics light up the neutral current indicator
Test Your Knowledge
See if you can answer these based on what you just learned.