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Harmonics Analysis

The Harmonics screen provides a detailed frequency-domain analysis of the voltage and current waveforms. Access it from the Waveforms > Harmonics section.

[Screenshot: Harmonics analysis screen with bar chart]

Harmonic Spectrum Display

ESP-GUARDX analyzes harmonics up to the 50th harmonic (e.g., up to 3,000 Hz on a 60 Hz system). The display shows:

  • Bar chart of individual harmonic magnitudes (as a percentage of the fundamental)
  • Fundamental frequency component (1st harmonic = 100% reference)
  • Per-phase breakdown -- Harmonics for each of the three phases

Key Harmonic Orders

Harmonic Frequency (at 60 Hz) Common Source
1st 60 Hz Fundamental (power supply)
3rd 180 Hz Single-phase nonlinear loads
5th 300 Hz 6-pulse VFD drives
7th 420 Hz 6-pulse VFD drives
11th 660 Hz 12-pulse VFD drives
13th 780 Hz 12-pulse VFD drives

THD Summary

At the top of the Harmonics screen, the following summary values are displayed:

  • Voltage THD (%) -- Per-phase and average
  • Current THD (%) -- Per-phase and average
Parameter IEEE 519 Limit
Voltage THD < 5%
Individual Voltage Harmonic < 3%
Current TDD Depends on ISC/IL ratio

IEC 61000-4-30 Compliance

The harmonic analysis engine implements:

  • Gapless window analysis -- No gaps between measurement windows, ensuring complete signal capture
  • 5th harmonic RMS buffering -- Smooth, stable 5th harmonic readings (critical for VFD monitoring)
  • Equation 2 calculations -- Standard-compliant harmonic magnitude computation
  • Pass/fail testing -- Automatic comparison against standard harmonic limits

Interpreting Harmonic Data

High Voltage THD

Indicates the power supply is distorted, which may be caused by:

  • VFD switching
  • Other nonlinear loads on the same bus
  • Transformer saturation

Action: Check VFD filter settings; consider adding line reactors or harmonic filters.

High Current THD

Indicates the motor is drawing non-sinusoidal current, which causes:

  • Additional motor heating (derating required)
  • Increased cable losses
  • Potential interference with protection relays

Action: Verify VFD pulse configuration; consider upgrading from 6-pulse to 12-pulse or 18-pulse.

[Screenshot: Detailed harmonic spectrum bar chart]