Current surge

Parallel resonant circuit

The term “ excessive current” is used when the current through a coil or capacitor in an oscillating circuit reaches a higher value than the current in the supply line.

This effect occurs in a parallel resonant circuit . Because of the parallel connection, the same voltage is applied to the coil and capacitor , but the sinusoidal currents have a phase shift of 180 ° in total (coil: 90 °, capacitor: −90 °).

With reactive power compensation , the connection of a capacitor to an inductive load ensures that the reactive currents in the supply line to the power grid do not become unnecessarily large.

The current increase is greatest at resonance and in this case proportional to the quality factor Q , i.e. an oscillating circuit with a quality of 100 has reactive currents of 100 amperes at resonance and an input current of one ampere.

${\displaystyle Q={\frac {I_{C}}{I}}\qquad mit\qquad I=I_{R}\qquad und\qquad I_{C}=I_{L}}$

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  Vector diagram of a parallel resonant circuit below the resonance frequency

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  Vector diagram of a parallel oscillating circuit at resonance

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  Vector diagram of a parallel resonant circuit above the resonance frequency

Related topics

The counterpart in the series resonant circuit is the voltage increase .