The increasing use of modern power electronic apparatus (drives, uninterruptible power supplies, etc) produces nonlinear current and thus influences and loads the network with harmonics (linepollution). The power factor correction or capacitance of the power capacitor forms a resonant circuit in conjunction with the feeding transformer. Experience shows that the selfresonant frequency of this circuit is typically between 250 and 500 Hz, i.e. in the region of the 5th and 7th harmonics.

Controllers for PFC are of major importance in the compensation system. They measure the actual power factor and connect or disconnect capacitor stages to achieve specific desired values (cos φ ). All types of the series feature menu-driven handling in plain language, various languages available. They are all panel-mounted types with an illuminated full graphic display HD-versions with OLED-display.

Conventional systems for power factor correction are used to optimize the power factor and reduce the level of harmonics in the grid. The usage of new technologies in modern industry has negative impacts on electric power quality of the main supply networks, e.g. frequent high load fluctuations and harmonic oscillation.