What is power factor correction?

Power factor correction (PFC) is the process of adding capacitors to an electrical system to reduce reactive power demand and bring the power factor closer to unity (1.0). This reduces current draw, lowers losses, and avoids utility penalties.

How do I calculate the capacitor size needed?

Qc = P × (tan φ1 − tan φ2), where P is active power in kW, φ1 = arccos(PF_current), φ2 = arccos(PF_target). The result Qc is in kVAR. For capacitance in μF: C = Qc × 10⁹ / (2π × f × V²).

What target power factor should I aim for?

Most utilities require PF ≥ 0.90 to avoid penalties. A target of 0.95–0.98 is recommended. Avoid overcorrecting above 1.0 (leading PF) as this can cause voltage rise and resonance issues.

What are the benefits of power factor correction?

Benefits include: reduced electricity bills (avoiding reactive power charges), lower current in cables (freeing capacity), reduced I²R losses, improved voltage regulation, and compliance with utility requirements.

Should I use fixed or automatic capacitor banks?

Fixed banks are suitable for constant loads (e.g., a single large motor). Automatic banks with contactors and a PF controller are better for varying loads — they switch capacitor steps on/off to maintain target PF.

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功率因數校正計算器

計算改善功率因數所需的電容組 kVAR 與 μF。Qc = P × (tan φ₁ − tan φ₂)。

kVAR 容量計算電容 μF 功率三角形

有功功率 P (kW)

目前功率因數 (cos φ₁)

目標功率因數 (cos φ₂)

系統電壓 (V, 線間電壓)

頻率 (Hz)

電容接法

快速預設

結果

所需電容組

—

每相電容值

—

校正前電流 (S₁ / I₁)

—

校正後電流 (S₂ / I₂)

—

電流降低量

—

無功功率補償

電容值 (μF)

範例 — 100 kW 負載，PF 0.75 → 0.95

tan φ₁ = tan(acos 0.75) = 0.8819, tan φ₂ = tan(acos 0.95) = 0.3287

Qc = 100 × (0.8819 − 0.3287) = 55.3 kVAR

⚠️ 注意： 請勿將功率因數過補償至超前（leading）狀態。這可能導致電壓上升、與變壓器產生共振，並損壞設備。

功率因數校正計算機 | 免費 kVAR & μF 工具

結果

無功功率補償

電容值 (μF)

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