Electrical systems • Displacement power factor
Estimate power-factor correction kVAR.
Calculate the theoretical reactive-power change between an existing lagging displacement power factor and a target value.
Step 2
Calculation result
Enter the measured values and complete the mandatory scope check.
Power-quality review required
No kVAR result is provided. Meaningful or uncertain nonlinear loads and harmonics can make this simplified displacement-PF method unsafe to apply. Obtain a harmonic survey and qualified power-quality review.
Theoretical correction
—Calculated reactive-power change; not equipment selection.The existing and target PF are equal, so the calculated correction is 0 kVAR.
- Existing reactive power Q₁
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- Target reactive power Q₂
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- Existing apparent power S₁
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- Target apparent power S₂
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Confirm measurements, load variation, network conditions, applicable standards, switching duty, protection and resonance risk before any installation decision.
The mathematical result is shown, but a target of exactly 1.00 can increase the risk of leading power factor under changing load. A qualified engineer must review the operating range and control approach.
Method and formula
For clean, near-sinusoidal conditions: φ₁ = acos(PF₁), φ₂ = acos(PF₂), Q₁ = P × tan(φ₁), Q₂ = P × tan(φ₂), and Qc = Q₁ − Q₂. Apparent powers are S₁ = P ÷ PF₁ and S₂ = P ÷ PF₂. With P in kW, reactive-power values are in kVAR and apparent-power values are in kVA.
Limits and interpretation
This is a steady-state displacement-power-factor calculation. It assumes lagging PF, constant active power and representative measurements. It does not model voltage, frequency, load steps, phase imbalance, harmonics, resonance, leading operation or equipment ratings. It performs no equipment, protection or installation design.
Why the harmonic gate fails closed
Power-electronic loads can introduce harmonic current, while power-factor correction equipment can be sensitive to harmonic conditions and resonance. “Yes” and “Not sure” therefore produce no kVAR value and require a power-quality assessment.