How big is the power factor (cos phi) of a frequency inverter? Does the use of reactive power compensation systems make sense for the correction of the power factor cos phi at a voltage source frequency inverter?

Answer:
The power factor at the current cuonsumnption of a frequency inverter is about 0.98 capacitive related to the fundamental component, i.e. almost 1.
Against this the power factor of an asynchronous motor connected at the output of the frequency inverter is inductive. This value is, however, for the interpretation of the power input of the frequency inverter without meaning.
Therefore, a drive axis consisting of frequency inverter and motor can (should) be set-up without a reactive-power compensation system, because this power factor cannot be changed.

Note:
Due to the nonlinear components (rectifiers) in the power input the frequency inverter takes in addition a so-called distortion reactive power which influences the power factor. The power factor correction for this nonlinear current consumption can be only especially made by effortful filters for harmonic. Such filters typically are used only at high requirements on the harmonic content of the power (low harmonic component current).

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