Capacitor Reactive Power Calculator (Q_c = 2πfCU²)

Capacitor Reactive Power Calculator (Q_c = 2πfCU²) | Online Free Tool | Elysia Tools

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category: Math & Numbers
Input types: select, number
Output type: json
Sample coverage: 4
API ready: Yes

Overview

Calculate the reactive power, capacitive reactance, and current of a capacitor using the standard formula Q_c = 2πfCU². This calculator supports single-phase, three-phase star (Y), and three-phase delta (Δ) connections, providing precise electrical engineering calculations for power systems.

When to use

When verifying the actual reactive power output of an existing capacitor bank under specific operating voltage and frequency conditions.
When calculating the capacitive reactance and current of a capacitor to ensure proper sizing of fuses, cables, and switchgear.
When analyzing three-phase power factor correction systems configured in either star (Y) or delta (Δ) topologies.

How it works

1Select the electrical connection type: single-phase, three-phase star (Y), or three-phase delta (Δ).
2Enter the capacitance value per phase (in Farads or Microfarads), the system frequency in Hertz, and the operating voltage.
3Click calculate to compute the capacitive reactance, phase current, and total reactive power in var and kvar.

Use cases

Determining the reactive power output of a legacy capacitor bank when relocated to a grid with a different voltage or frequency.
Calculating the current draw of a capacitor to select appropriate overcurrent protection devices.
Verifying the impedance and reactive power contribution of individual capacitor steps in an automatic power factor correction panel.

Examples

1. Single-Phase Capacitor Analysis

Electrical Maintenance Engineer

Background

An engineer needs to verify the current and reactive power of a 10 µF motor run capacitor operating on a 230 V, 50 Hz single-phase supply.

Problem

Manually calculating the capacitive reactance and current is time-consuming and prone to rounding errors.

How to use

Select 'Single phase' connection, enter 10 for capacitance, select 'µF', enter 50 for frequency, and 230 for voltage.

Outcome

The tool outputs a capacitive reactance of 318.3099 Ω, a current of 0.7226 A, and a reactive power of 166.1903 var.

2. Three-Phase Delta Capacitor Bank Verification

Power Quality Consultant

Background

A consultant is inspecting an industrial facility's power factor correction panel containing delta-connected capacitor steps of 50 µF per phase at 400 V, 50 Hz.

Problem

The consultant needs to determine the total kvar output of the step to verify if it matches the nameplate rating.

How to use

Select 'Three-phase Delta (Δ)' connection, enter 50 for capacitance, select 'µF', enter 50 for frequency, and 400 for voltage.

FAQ

What formula is used to calculate the reactive power?

The calculator uses Q_c = 2πfCU² for single-phase, Q_c = 3·2πfC(U_LL/√3)² for three-phase star, and Q_c = 3·2πfCU_LL² for three-phase delta.

What is the difference between line-to-line and phase voltage in this calculator?

For single-phase connections, enter the phase voltage. For three-phase star or delta connections, enter the line-to-line voltage.

Can I input capacitance in microfarads (µF)?

Yes, the calculator supports both Farads (F) and Microfarads (µF) as input units.

How does connection type affect the reactive power output?

A delta connection produces three times more reactive power than a star connection for the same per-phase capacitance and line-to-line voltage.

Does this tool calculate the required capacitance for a target power factor?

No, this tool calculates the output of a known capacitor. Use a power factor correction tool to size a capacitor for a target cosφ.

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Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Overview

When to use

How it works

Use cases

Examples

1. Single-Phase Capacitor Analysis

2. Three-Phase Delta Capacitor Bank Verification

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