Motor Speed Calculator Formula
Understand the math behind the motor speed calculator. Each variable explained with a worked example.
Formulas Used
Synchronous Speed
synchronous_speed = sync_speedActual Rotor Speed
actual_speed = sync_speed * (1 - slip / 100)Variables
| Variable | Description | Default |
|---|---|---|
frequency | Supply Frequency(Hz) | 50 |
poles | Number of Poles | 4 |
slip | Slip at Full Load(%) | 3 |
sync_speed | Derived value= 120 * frequency / poles | calculated |
How It Works
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.
Worked Example
A 4-pole motor on 50 Hz supply with 3% slip at full load.
frequency = 50poles = 4slip = 3
- 01Synchronous speed = 120 x 50 / 4 = 1500 RPM
- 02Actual speed = 1500 x (1 - 0.03) = 1455 RPM
Ready to run the numbers?
Open Motor Speed Calculator