Line Reactors For VFDs
Protecting a variable frequency drive (VFD) from input power line disturbances involves smoothing and slowing down the types of voltage distortions that can happen in power lines. Line reactors do this by controlling the currents into VFDs, controlling the size of inlet currents for a given set of conditions. Higher inlet currents can starve the VFD of essential drive power, especially during high motor current demand situations like startup or acceleration when both current and voltage are at their peak values.
The VFD current waveform is kept stable by the line reactor. Acting as an impedance, it also serves to protect the power supply section of the VFD and reduce the amount of harmonics that commonly plague three-phase systems.
The applied impedance of the VFD line reactor softens and slows down the incoming line voltage distortion, like power system surges and voltage spikes when it's on the input side of a VFD. This is to prevent over-voltage faults in the VFD's inputs. Being on the input side means that it can see all kinds of bad things happening with the line voltage—surgically removing distortions of any kind that might occur within the power system as seen by the VFD.
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