Harmonic distortion indicators - Crest factor: Difference between revisions
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== Definition == | |||
The crest factor is the ratio between the value of the peak current or voltage (Im or Um) and its rms value. | The crest factor is the ratio between the value of the peak current or voltage (Im or Um) and its rms value. | ||
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In the latter case, the crest factor signals divergent peak values with respect to the RMS value.<br> | In the latter case, the crest factor signals divergent peak values with respect to the RMS value.<br> | ||
== Interpretation of the crest factor == | |||
The typical crest factor for the current drawn by non-linear loads is much higher than <math>\sqrt2</math> It is generally between 1.5 and 2 and can even reach 5 in critical cases. A high crest factor signals high transient overcurrents which, when detected by protection devices, can cause nuisance tripping. | The typical crest factor for the current drawn by non-linear loads is much higher than <math>\sqrt2</math> It is generally between 1.5 and 2 and can even reach 5 in critical cases. A high crest factor signals high transient overcurrents which, when detected by protection devices, can cause nuisance tripping. | ||
Revision as of 08:57, 16 June 2011
Definition
The crest factor is the ratio between the value of the peak current or voltage (Im or Um) and its rms value.
- For a sinusoidal signal, the crest factor is therefore equal to [math]\displaystyle{ \sqrt 2 }[/math].
- For a non-sinusoidal signal, the crest factor can be either greater than or less than [math]\displaystyle{ \sqrt2 }[/math].
In the latter case, the crest factor signals divergent peak values with respect to the RMS value.
Interpretation of the crest factor
The typical crest factor for the current drawn by non-linear loads is much higher than [math]\displaystyle{ \sqrt2 }[/math] It is generally between 1.5 and 2 and can even reach 5 in critical cases. A high crest factor signals high transient overcurrents which, when detected by protection devices, can cause nuisance tripping.
