Contactors for Capacitor Switching With Insertion Of Damping Resistors

When choosing switching contactors for capacitors used to compensate the reactive power present in the network, you should bear several aspects in mind

  • On being energized the capacitor is connected in parallel to the inductive network and the oscillating circuit produced by connecting the capacitor to the network will result in the passage of a high-frequency current (from 3 to 15 kHz), which may be 160 times greater than the In current for 1 or 2 ms
  •  The presence of harmonic currents and the tolerance with respect to mains voltage determine the continuous passage, within the circuit, of a current whose value is around 1.3 times greater than the rated current In of the capacitor
  • Because of the tolerances allowed by the manufacturer, the exact power of a capacitor may be 1.10 times greater than the rated power.

The contactor must be capable of working with:

  • An elevated, albeit transient, peak current during the closing phase.
  • A closing current that may be 1.43 times greater than the rated current of the capacitor

The contactors offered by DUCATI Energia are specifically engineered to work in these conditions. Select the type of contactor based on the working voltage and effective power (in kVAr) of the capacitor bank to be controlled.

Contactors within banked or group PFC systems are typically in close proximity to low-impedance capacitors that are already charged. The short wire lengths add little impedance to the charge path letting charged, low-impedance capacitors combine with the power source to produce inrush currents that exceed the ratings of normal contactors.


Part Number kVAr 50/60 Hz  ∂ ≤ 55°C (*) Aux Contacts Maximum Operating Frequency – Switching per hour Electric life with rated load Switching
200 V
240 V
400 V
440 V
1143 6.7 12.5 1 1 240 200000
1142 10 20 1 1 240 100000
1141 15 25 1 1 240 100000
1140 20 40 1 2 100 100000
1139 40 60 1 2 100 100000
(*) Average temperature over 24h as per standards IEC 70 and 851.
230 VAC 50/60 Hz coil for all sizes.
WARNING: The capacitors must be completely discharged before
being energized by closing contacts (max voltage at terminals < 50 V)