Capacitor Bank Sizing & Resonance Risk
Sizing of power factor correction capacitance together with the resonance check that must accompany it. A capacitor bank and the supply inductance form a resonant circuit; if that resonance lands near a harmonic the load produces, the result is amplification rather than correction.
What this study establishes.
Reactive compensation sizing to reach the target power factor across the load range.
Parallel resonance frequency calculation for each switching step, not just the full bank.
Frequency scan showing impedance against order, with amplification bands identified.
Detuned reactor recommendation with the detuning factor selected against the site spectrum.
Step and switching strategy — fixed, automatic, or thyristor-switched for fast-changing load.
Capacitor duty check against harmonic current and the overload allowance.
What the work covers.
Sizing of power factor correction capacitance together with the resonance check that must accompany it. A capacitor bank and the supply inductance form a resonant circuit; if that resonance lands near a harmonic the load produces, the result is amplification rather than correction.
The resonant frequency shifts with every switching step and with the supply configuration. Checking only the fully-connected bank is a common omission — an intermediate step frequently lands closer to the 5th or 7th than the full bank does.
What lands in your inbox.
Reactive compensation sizing to reach the target
Reactive compensation sizing to reach the target power factor across the load range.
Parallel resonance frequency calculation for each switching
Parallel resonance frequency calculation for each switching step, not just the full bank.
Frequency scan showing impedance against order,
Frequency scan showing impedance against order, with amplification bands identified.
Detuned reactor recommendation
Detuned reactor recommendation with the detuning factor selected against the site spectrum.
Step and switching strategy
Step and switching strategy — fixed, automatic, or thyristor-switched for fast-changing load.
Capacitor duty check against harmonic current and
Capacitor duty check against harmonic current and the overload allowance.
How we run it.
Scope & data capture
We confirm the question the study must answer, agree the measurement or modelling points, and collect what the work depends on: measured power factor profile across the day and the target to be achieved; harmonic spectrum at the board where the bank will connect; transformer impedance and rating, which set the resonance.
Measurement & modelling
Engineers carry out the measurement and modelling on site and in software, under operating conditions representative of the problem rather than a single convenient snapshot.
Analysis against standard
Results are assessed against IEEE 1036, IEC 61921, IEC 60831-1, with the assessment basis and any measurement uncertainty stated rather than implied.
Report & recommendations
You receive a signed engineering report with findings ranked by consequence, the reasoning behind each conclusion, and mitigation options costed so they can be acted on or deferred deliberately.
Assessed against the published limits.
Common questions.
Typically in one of these situations: utility is applying a reactive power or low power factor penalty; existing capacitor bank is failing, blowing fuses or bulging; adding capacitance to a site with significant non-linear load. If none of these apply, the study is unlikely to be the right next step and we will say so.
To scope and run the work we need measured power factor profile across the day and the target to be achieved; harmonic spectrum at the board where the bank will connect; transformer impedance and rating, which set the resonance frequency with the bank. Where any of it is missing we can establish it on site, which changes the scope rather than blocking the work.
Primarily IEEE 1036, IEC 61921, IEC 60831-1, IEC 61642. The applicable framework depends on your connection agreement and jurisdiction, so we confirm which applies before measurement rather than after.
Ready to start the engagement?
Tell us about your site and the problem you are seeing. We come back with a fixed scope, a fixed fee, and a named lead engineer.