Dynamic power factor correction

Dynamic (fast) PFC

Dynamic PFC systems

Dynamic PFC systems are particularly used in applications with rapid and high load changes. In such cases, conventional PFC systems are not fast enough to follow the load changes which means that these systems are either undercompensated or overcompensated.

Electromechanical protectors are not suitable for these types of frequent switching cycles. If contactors or capacitor contactors are still used in such applications, the contactors are worn out very quickly and this can lead to significant safety risks for the whole system.


Dynamic PFC systems avoid this problem with the help of semiconductors. Semiconductors gently connect the capacitors to the network i.e. without network perturbations and and without stresses for different components like capacitors, fuses or contractors. By the gentle connect the negative effects on the power quality, which usually occur Through high inrush currents, are avoided.

This results in the following advantages:

  • Improved power quality i.e. high inrush currents from power capacitors are avoided
  • The lifespan of PFC systems is increased
  • The safety of the full system is significantly increased (i.e. damages due to defective contactors and as a result of exploding capacitors are avoided)
  • Extremely rapid regulation of the power factor and therefore consequential reduction of reactive power costs and kWh losses
  • Voltage stabilisation (e.g. network support during the start-up phase for large motors)
  • Improved utilization for energy distribution (transformers, cable, switch gear etc.) through the elimination of power peaks
  • Process times can be shortened (e.g. welding)

Dynamic PFC systems are typically used in following applications:

  • Automotive industry (welding, presses, …)
  • Lift and cranes
  • Large motor start-up compensation
  • Crude oil drilling
  • Wind turbines
  • Welding
  • Rolling mills
  • Plastic extrusion

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