Motor Speed Calculator
Calculate the synchronous speed and estimated actual speed of an AC induction motor.
Actual Rotor Speed
1,455 RPM
Actual Rotor Speed vs Supply Frequency
Formule
## AC Induction Motor Speed The speed of an induction motor depends on the supply frequency, number of poles, and load-dependent slip. ### Formulas **N_sync = 120 f / P** (synchronous speed) **N_actual = N_sync (1 - s)** (actual speed) where f is the supply frequency in Hz, P is the number of poles, and s is the slip (as a decimal). Synchronous speed is the rotating magnetic field speed. The rotor always turns slightly slower.
Exemple Résolu
A 4-pole motor on 50 Hz supply with 3% slip at full load.
- 01Synchronous speed = 120 x 50 / 4 = 1500 RPM
- 02Actual speed = 1500 x (1 - 0.03) = 1455 RPM
Questions Fréquentes
What is slip in an induction motor?
Slip is the difference between synchronous speed and actual rotor speed, expressed as a percentage. Typical full-load slip is 2-5% for standard motors. Without slip, no torque would be produced because no relative motion would exist between rotor and stator fields.
How many poles for common motor speeds?
At 50 Hz: 2-pole = 3000 RPM, 4-pole = 1500 RPM, 6-pole = 1000 RPM, 8-pole = 750 RPM. At 60 Hz: 2-pole = 3600, 4-pole = 1800, 6-pole = 1200.
Can I change motor speed?
Yes. Variable frequency drives (VFDs) change the supply frequency to control speed continuously. Multiple-speed motors have switchable pole configurations. Mechanical speed changes use gearboxes or pulleys.
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