Industrial Engineer · phase 13 of 16 · noun

Harmonics

Current or voltage components at integer multiples of the fundamental frequency that distort the supply waveform.

The Explain card

Plain English: Harmonics are currents and voltages at whole number multiples of the line frequency, riding on top of the fundamental. A drive's diode front end draws current in pulses rather than in a sine, and pulses are full of harmonics.
Example: A plant with a dozen large drives sees fifth and seventh harmonic currents on its feeders. The transformer runs warm, the power factor correction capacitors hum, and a sensitive meter reads wrong.
Why it matters: Harmonics heat transformers and cables, trip breakers on current they were never sized for, and can violate the utility's limits at the service entrance. Reactors, multipulse rectifiers and active front ends exist to reduce them.
Hook: The distortion the drive sends back up the wire.

How the word is built, where it came from, and what it sits beside in memory.

In a sentence

During VFD commissioning, the engineer measured harmonics at the drive input with a power-quality analyzer.

How it is built

Where it came from

Origin: English harmonics from harmonic, through Latin harmonicus from Greek harmonikos, based on harmonia, joining or agreement
Entered the language: 19th century
What changed: The word moved from musical concord to members of a frequency series, then entered electrical engineering usage.

How it is spelled

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Broken into chunks

What it sits beside

Same subject

Same shape

power-quality phenomena

harmonic orders

Phase 13: VFD Power Quality, Wiring, and Motor Protection

Harmonics, reflected waves, shielded cable and bearing currents: the side effects a drive inflicts on everything around it.