Harmonics Calculator | Calctra

📊 Harmonics Calculator (VTHD & ITHD)

Estimate Voltage THD and Current THD for different electrical loads using this free Harmonics Calculator by Calctra.

Select Load Type Connected Load (kW) System Voltage (V)

📐 Formula Used

Voltage THD (VTHD)

VTHD (%) = √(V₂² + V₃² + … + Vn²) ÷ V₁ × 100

Current THD (ITHD)

ITHD (%) = √(I₂² + I₃² + … + In²) ÷ I₁ × 100

Note: This calculator uses typical industry-average harmonic values for estimation.

📘 What are Harmonics?

Harmonics are voltage and current distortions in electrical systems caused by non-linear loads. These distortions create frequencies that are multiples of the fundamental frequency (50 Hz in India).

Non-linear devices draw current in pulses instead of smooth sinusoidal waves, producing harmonics.

Common Harmonic Orders

3rd Harmonic – Neutral overheating
5th Harmonic – Motor heating
7th Harmonic – Torque pulsation
11th & 13th – Equipment stress

📝 Example

Load Type: VFD Drive

Load: 50 kW

Voltage: 415 V

Result:

VTHD ≈ 6.5%

ITHD ≈ 38%

Status: High Harmonics

💡 Use Cases & Applications

Power quality analysis
Substation and panel design
Energy audits
Industrial maintenance
Transformer sizing
DG set protection

❓ FAQ

Q1. What is safe THD level?

As per IEEE-519 standard, VTHD should be below 5%.

Q2. Which loads create maximum harmonics?

VFDs, SMPS, UPS, and LED drivers generate high harmonics.

Q3. How to reduce harmonics?

Use harmonic filters, detuned reactors, and active filters.

Q4. Does harmonics affect DG sets?

Yes, high harmonics cause overheating and voltage instability.

Q5. Can harmonics increase electricity bill?

Indirectly yes, due to losses and reduced efficiency.