Power factor correction basics in Australian power work
How Australian power factor correction estimates use existing PF, target PF, kW basis, kVAr and power-quality context.
What correction estimates do
In Australian power work, power factor correction is the planning topic of improving a load's power factor, often by adding correction equipment such as a capacitor-bank arrangement. A calculator can estimate required kVAr from entered values, but that estimate is not the same as selecting equipment for a live site.
The core inputs are existing power factor, target power factor and the kW basis for the load. The result is usually a correction kVAr value that needs power-quality and equipment review before any project action.
Formula basis to keep visible
A common correction relationship is:
correction kVAr = kW x (tan phi existing - tan phi target)
where tan phi existing = tan(arccos(existing PF)) and tan phi target = tan(arccos(target PF)).
For example, improving a 100 kW load from PF 0.80 to PF 0.95 gives about 42 kVAr of correction. The number changes if the kW basis, existing PF or target PF changes.
The same relationship can be read as the difference between existing kVAr and target kVAr. That before-and-after comparison should stay with the 230/400 V, 50 Hz load context, utility or tariff reason, and manufacturer review notes.
| Input | What it describes | Why it matters |
|---|---|---|
| Existing PF | Measured, metered or assumed starting value. | The estimate changes if the starting value changes. |
| Target PF | Entered comparison target. | The target may be controlled by tariff, utility or engineering context. |
| kW basis | Load level used for the estimate. | Correction kVAr depends on the load basis. |
| Power-quality context | Harmonics, resonance risk, switching and equipment data. | Correction equipment can interact with site conditions. |
Estimate workflow
| Step | Keep visible | Stop point |
|---|---|---|
| Estimate kVAr | Existing PF, target PF and kW basis. | Use the correction calculator for the arithmetic. |
| Screen conditions | Harmonics, resonance risk, switching duty and utility context. | Do not select equipment from kVAr alone. |
| Review equipment | Manufacturer data, site measurements and project requirements. | Qualified review controls equipment selection. |
| Document decision | Final equipment, protection, switching and maintenance context. | Keep the project file traceable. |
The power-factor relationship chart helps explain why kW, kVA, kVAr and PF move together. It does not replace a correction study, manufacturer instruction or utility requirement.
Next checks
- If the existing PF is only assumed, label it clearly before estimating correction.
- If the target PF comes from a tariff, utility or project requirement, keep that source beside the result.
- If harmonics, resonance or switching duty could matter, screen those issues before equipment selection.
- If the work moves from estimate to installation, use manufacturer data, qualified review and licensed electrical work.
Boundaries
- A correction estimate does not select capacitor equipment.
- It does not assess harmonics, resonance, switching behaviour or protection requirements.
- It does not guarantee utility acceptance or tariff outcome.
- Manufacturer data, utility requirements, metering data and engineering review can control the final decision.