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Motor Speed & Torque Calculator

Synchronous Speed · Slip · Shaft Torque

Calculate synchronous speed, actual rotor speed, slip and shaft torque for AC induction motors based on supply frequency, number of poles and rated power. Useful for motor selection, gearbox ratio calculations, and understanding motor performance characteristics.

CALCULATOR

Speed & Torque

0% (sync)2–4% (typical)10%
SYNCHRONOUS SPEED
1500
RPM
ROTOR SPEED
1455
RPM
Slip Speed45 RPM (3%)
Enter motor power above to calculate torque

Results for guidance only. Verify against current standards and manufacturer data.
Not a substitute for engineering judgement or a licensed professional.

Methodology

Synchronous speed is fixed by supply frequency and pole count: Ns = 120f/P. Actual rotor speed is always slightly lower due to slip — the difference between the rotating magnetic field speed and rotor speed that induces current in the rotor windings. Shaft torque is derived from power and angular velocity: T = P/(ω), where ω = 2πN/60.

Assumptions & Limitations

  • Slip is user-specified — verify against motor nameplate rated speed for accurate results
  • Torque calculated is running (rated) torque, not starting or breakdown torque

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Built with reference to AS/NZS 3000, AS/NZS 3008, AS/NZS 1359
Results for guidance only — not a substitute for engineering judgement
Does not reproduce copyrighted Standards Australia material. Always consult current standards for compliance.