Damping reactors are typically Air-Core reactors and used for damping transients and inrush currents.

The percentage tuning factor of these reactors ranges between 0.2 to 1%. The percentage tuning factor, p is defined as the ratio of the inductive reactance(Xl) to the capacitive reactance(Xc) at a nominal system frequency of 50Hz.

When connected in series with the capacitor, the reactor reduces the inrush peak current into the capacitor to a value which cannot stress the insulation and does not damage the internal connections of the capacitor elements.