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Motor from three-phase to single-phase

V
Hz
Description

This tool calculates the running and starting capacitor values needed to operate a three-phase induction motor on single-phase power. Suitable for small motors (< 1.5 kW), with output power reduced to 60–70%.

Input motor rated power, single-phase voltage, and frequency to automatically calculate:

  • Running capacitor (μF)
  • Starting capacitor (μF)
  • Supports kW and hp units
  • Real-time bidirectional calculation

Key Formulas

Running Capacitor: C_run = (2800 × P) / (V² × f)
Starting Capacitor: C_start = 2.5 × C_run
Where:
P: Motor power (kW)
V: Single-phase voltage (V)
f: Frequency (Hz)

Example Calculations

Example 1:
1.1 kW motor, 230 V, 50 Hz →
C_run = (2800 × 1.1) / (230² × 50) ≈ 11.65 μF
C_start = 2.5 × 11.65 ≈ 29.1 μF

Example 2:
0.75 kW motor, 110 V, 60 Hz →
C_run = (2800 × 0.75) / (110² × 60) ≈ 2.9 μF
C_start = 2.5 × 2.9 ≈ 7.25 μF

Important Notes

  • Only suitable for small motors (< 1.5 kW)
  • Output power drops to 60–70% of original
  • Use capacitors rated at 400V AC or higher
  • Starting capacitor must be automatically disconnected
  • Motor should be connected in "Y" configuration

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