Induction Motor Slip Calculator
A 4-pole, 50 Hz motor at 1440 rpm runs at a slip of 4 %: the synchronous speed is 1500 rpm and rotor currents alternate at 2 Hz.
Power crossing to the rotor; 0 to skip the power split.
4 %
- Synchronous speed Nₛ = 120f/P
- 1500 rpm
- Slip speed Nₛ − N
- 60 rpm
- Rotor current frequency sf
- 2 Hz
- Rotor copper loss s × P_ag
- 0.4 kW
- Mechanical power (1 − s) P_ag
- 9.6 kW
- Torque P_ag ÷ ωₛ
- 63.66197724 N·m
- Mode
- motoring
Step-by-step solution
- Nₛ = 120f ÷ P = 120 × 50 ÷ 4 = 1500 rpm
- s = (Nₛ − N) ÷ Nₛ = (1500 − 1440) ÷ 1500 = 0.04
- Rotor frequency = s f = 2 Hz
Induction Motor Slip Formula
Nₛ = 120f/P, s = (Nₛ − N)/Nₛ
rotor frequency sf; rotor copper loss = sP_ag; mechanical power = (1 − s)P_ag
Worked Example
A 4-pole, 50 Hz motor running at 1440 rpm with 10 kW crossing the air gap:
- Nₛ = 120f ÷ P = 120 × 50 ÷ 4 = 1500 rpm
- s = (Nₛ − N) ÷ Nₛ = (1500 − 1440) ÷ 1500 = 0.04
- Rotor frequency = s f = 2 Hz
Slip speed Nₛ − N: 60 rpm · Rotor current frequency sf: 2 Hz · Rotor copper loss s × P_ag: 0.4 kW · Mechanical power (1 − s) P_ag: 9.6 kW · Torque P_ag ÷ ωₛ: 63.66197724 N·m · Mode: motoring
GATE tip
Maximum torque occurs at slip s = R₂/X₂ and does not depend on rotor resistance in value, only in position. Starting torque is maximum when R₂ = X₂.
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Frequently asked questions
Why can an induction motor never reach synchronous speed?
At Nₛ the rotor sees no changing flux, so no current is induced and no torque is produced. Some slip is always needed to carry load.
What is the power split?
Of the air-gap power P_ag, a fraction s is lost as rotor copper loss and (1 − s) becomes mechanical power: P_ag : P_cu2 : P_mech = 1 : s : (1 − s).
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
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APA
Scientific Converters. (2026, October 15). Induction Motor Slip Calculator. Retrieved October 25, 2026, from https://scientificconverters.com/calculators/induction-motor-calculator/
IEEE
Scientific Converters, "Induction Motor Slip Calculator," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/calculators/induction-motor-calculator/