🔍 /

3-Phase Motor Capacitor Sizing (Steinmetz)

Calculate the required Run and Start capacitors to operate a 3-phase motor on a single-phase power supply using the Steinmetz connection.

User Rating 0.0 ★★★★★
Total Usage 1 times
Category Electronics
Run Capacitor0 µF
Start Capacitor0 µF
MotorLNC
Is this tool helpful?

Your feedback helps us improve.

★ ★ ★ ★ ★

About

Running a 3-phase asynchronous motor on a single-phase supply (household outlet) is possible using the Steinmetz Connection. This method uses a capacitor to create a phase shift, simulating a third phase. While this allows the motor to run, it typically results in a torque reduction of ~30%.

This tool calculates the optimal Run Capacitor to maintain the rotating magnetic field and estimates a Start Capacitor for high-torque applications. Incorrect sizing can lead to motor overheating or failure to start.

steinmetz circuit motor capacitor 3 phase to 1 phase electronics calculator run capacitor

Formulas

The empirical formula for the Working (Run) Capacitor Crun on a 220-240V network:

Crun ≈ 70 ⋅ PkW

Alternatively, using current:

C = 50 × IU × f (Simplified)

Reference Data

ParameterValueUnit
ConnectionDelta (Δ)For 230V Supply
Run Capacitor70 per kWµF
Start Capacitor2.5 × Run CapµF
Efficiency Loss20-30%Power

Frequently Asked Questions

Generally, yes, if the motor is rated for 230V/400V. You must connect the windings in Delta (Δ) for 230V single-phase use. If the motor is only rated 400V/690V, you cannot use this method efficiently on standard household power.
A capacitor that is too large allows excessive current to flow through the auxiliary winding, causing the motor to overheat rapidly and potentially burn out.