PFC Panels That Cut Reactive Demand and Penalties

Inductive loads such as motors and transformers draw reactive power that does no useful work but loads the supply, increasing losses and, in many tariffs, attracting charges for poor power factor. Power factor correction adds capacitive compensation to bring the power factor closer to unity, reducing the current drawn for the same useful work.

Exa Power builds automatic and fixed PFC panels on authorized ABB systems, engineered and verified to IEC 61439. Automatic panels switch capacitor steps in and out as the load varies, holding the target power factor across changing conditions, while fixed panels suit steady loads where the reactive demand is largely constant.

Correctly applied, power factor correction is one of the most cost-effective electrical improvements available: it reduces a recurring charge, frees up capacity in the existing installation, and improves voltage conditions, often with a short payback.

The right type of PFC depends on how the reactive demand behaves over time. Where the load is reasonably steady, for example a transformer or a continuously running motor, fixed compensation sized to that demand is simple and effective. Where the load varies through the day, as it does in most commercial and many industrial installations, fixed compensation would over-correct at light load and under-correct at peak, so automatic correction is used instead. An automatic panel switches capacitor steps in and out under the control of a power factor regulator, holding the target as the load rises and falls.

The number and size of the steps is itself a design choice. Too few coarse steps and the regulator cannot track the load closely; too many small steps and the contactors switch unnecessarily often, wearing themselves and the capacitors. We choose the step arrangement and regulator settings so the panel holds the target power factor smoothly across the load range while keeping switching, and therefore wear, to a sensible level.

Modern installations are full of electronic loads such as variable frequency drives, UPS systems, LED lighting and IT equipment, all of which inject harmonic currents into the network. Capacitors present a low impedance to higher frequencies, so in a harmonic-rich installation a plain capacitor bank can draw excessive harmonic current, overheat, age prematurely, and in the worst case resonate with the supply transformer and amplify the very harmonics it is exposed to.

The remedy is detuning. By connecting a reactor in series with each capacitor step, the resonant frequency of the bank is shifted below the lowest significant harmonic, so the bank cannot resonate at a harmonic frequency and the capacitors are protected from excessive current. We assess the harmonic environment from the load profile and known non-linear loads, then specify detuned banks where they are warranted.

Where harmonics are severe, detuning may be combined with other mitigation; we advise on the appropriate approach based on the data you provide rather than applying a one-size-fits-all solution.