Induction Motor Slip

Enter line frequency and poles, then add either rotor RPM or slip to solve instantly. Includes synchronous speed, slip %, rotor speed, and optional slip frequency.

How to Use

  1. Pick a common preset (optional).
  2. Enter Line Frequency and Poles (or synchronous RPM if you already know it).
  3. Enter either Rotor Speed (RPM) or Slip (%).
  4. Open Show Work to see formulas and steps.
Speed View
Synchronous vs rotor speed + slip indicator.
Ns
—
Nr
—
Slip
—
f₂
—
Slip band: —

Typical full-load slip is often a few percent on many induction motors (varies by design/load).

Inputs & Settings
Enter frequency + poles, then add rotor RPM or slip. Tool solves the rest.
Common: 50 Hz, 60 Hz
Most common: 2, 4, 6, 8
Enter an even number (typical).
If provided, overrides Hz+poles for Ns.
If you know rotor RPM, slip is computed.
If you know slip %, rotor RPM is computed.
Show Work (step-by-step)
—
Work is shown using: Hz, poles, RPM, and slip as a decimal fraction.

Formulas

  • Synchronous speed: Ns = 120 × f / P (RPM)
  • Slip (decimal): s = (Ns − Nr) / Ns
  • Slip (%): Slip% = s × 100
  • Rotor speed: Nr = Ns × (1 − s)
  • Slip frequency (optional): f₂ = s × f (Hz)
Where f = line frequency (Hz), P = poles, Ns = synchronous RPM, Nr = rotor RPM, s = slip fraction.

FAQ

What does “slip” mean?

Slip is how much slower the rotor turns compared to synchronous speed. Induction motors require slip to produce torque.

Why is synchronous speed based on 120?

It comes from converting electrical cycles (Hz) into mechanical RPM, factoring the number of poles in the rotating field.

Can slip be 0%?

In real induction motors under load, slip is not exactly 0%. Near no-load, it can be very small.

What if my measured RPM is higher than Ns?

That implies negative slip (generator action) or a measurement/inputs mismatch. This tool flags it as a special case.

Tool Info

Last updated:

Updates may include UI refinements, additional motor presets, and edge-case handling.