Single Phase Motor Capacitor Calculator

How to Calculate Single-Phase Motor Capacitor

The Single-Phase Motor Capacitor Calculator computes the capacitance C in microfarads (µF) based on power P (in W, HP, or kW), efficiency η, voltage V, and frequency f. The formula is:

\( C(\mu F) = \frac{P(W) \times \eta \times 1000}{V(V) \times V(V) \times f(Hz)} \)

Where P(W) is converted from HP (×746) or kW (×1000) if needed.

Where:

\( C \): Capacitance in microfarads (µF).
\( P(W) \): Power in watts (W).
\( \eta \): Efficiency as a decimal (e.g., 0.85 for 85%).
\( V(V) \): Voltage in volts (V).
\( f(Hz) \): Frequency in hertz (Hz).
1000: Conversion factor.

Enter the power, unit, efficiency, voltage, and frequency to calculate the capacitance.

Using the Single-Phase Motor Capacitor Calculator

This calculator is useful for determining the capacitor size for single-phase motors, such as in run or start applications.

Input the power, select the unit (W, HP, kW), efficiency (default: 0.85), voltage, and frequency (default: 60 Hz). The calculator outputs the capacitance in µF.

Example: Calculate capacitor for a 1 HP motor at 220 V, 50 Hz, 0.85 efficiency.

Power: \( 1 \, \text{HP} = 746 \, \text{W} \)
Voltage: \( 220 \, \text{V} \)
Frequency: \( 50 \, \text{Hz} \)
Calculation: \( C = \frac{746 \times 0.85 \times 1000}{220 \times 220 \times 50} = 0.262 \, \mu F \)
Result: \( 0.262 \, \mu F \)

Use this tool for motor capacitor sizing in electrical design.

Common FAQ

Below are frequently asked questions about Single-Phase Motor Capacitor calculations:

Q: What is the purpose of the capacitor in a single-phase motor?
A: It provides phase shift for starting or running torque in induction motors.
Q: Why is capacitance proportional to power?
A: Larger motors require more reactive power compensation, increasing capacitor size.
Q: How accurate is this calculator?
A: It uses the provided formula with precise conversions, rounded to 3 decimal places.
Q: Can negative values be used?
A: No, inputs must be positive; invalid inputs return an error.
Q: What if efficiency is unknown?
A: Use typical value (0.85) or consult motor specifications.