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Motor Slip Calculator — Synchronous Speed, RPM & Rotor Frequency

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Supply frequency (Hz) Use actual VFD output frequency when applicable.Motor poles Even whole-number pole count.Measured rotor speed (rpm) Measured shaft speed at the same operating point.Nameplate full-load RPM (optional) Enter 0 to omit rated-slip comparison.

Calculated result

2.778% slip

Synchronous speed: 1,800 rpm

Slip speed: 50 rpm

Rotor electrical frequency magnitude: 1.667 Hz

Rotor speed: 97.222% of synchronous

Positive motoring slip.

No nameplate full-load RPM entered; rated-slip comparison omitted.

Show the working

1. Ns = 120 × 60 ÷ 4 = 1,800 rpm.
2. Slip speed = 1,800 − 1,750 = 50 rpm.
3. Slip = (1,800 − 1,750) ÷ 1,800 × 100 = 2.778%.
4. Rotor frequency magnitude = |0.027778| × 60 = 1.667 Hz.

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