AC Induction Motor Diagnostics

Motor Synchronous Speed & Slip Calculator

VFD drive setup, motor troubleshooting, checking mechanical motor overload. Calculates synchronous magnetic field RPM, actual rotor RPM, and percentage slip for AC induction motors.

Motor Synchronous Speed & Slip Calculator
Hz
Poles
RPM
Calculated Result
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Instant Calculation
Engineering Output
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Auxiliary Output
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Step-by-Step Derivation ▼ Show Steps
Governing Formula Verified Physics
Ns = (120 × f) / Poles  |  Slip % = [(Ns - Nr) / Ns] × 100

Calculations adhere to standard electrical engineering physics and National Electrical Code (NFPA 70) regulations.

Engineering Principles & Calculations

This calculator uses the exact mathematical relationships between Frequency (50Hz / 60Hz), Number of Poles (2, 4, 6, 8, 12), Measured Rotor RPM (Nr) to determine Synchronous Speed (RPM), Motor Slip (%), Rotor Frequency (Hz). In practical installations, factors such as ambient raceway temperature, harmonic distortion, duty cycle continuous operation, and conductor impedance must be accounted for by a certified electrician.

Calculates synchronous magnetic field RPM, actual rotor RPM, and percentage slip for AC induction motors.

Typical Application & Industry Guidelines

VFD drive setup, motor troubleshooting, checking mechanical motor overload.

Reference Matrix

Motor Synchronous Speed & Slip Calculator Benchmark Lookup Table

Stator Poles60Hz Synchronous (RPM)60Hz Full Load (RPM)50Hz Synchronous (RPM)50Hz Full Load (RPM)
2 Poles3600 RPM3450 - 3520 RPM3000 RPM2850 - 2920 RPM
4 Poles (Most Common)1800 RPM1725 - 1765 RPM1500 RPM1425 - 1465 RPM
6 Poles1200 RPM1140 - 1170 RPM1000 RPM940 - 970 RPM
8 Poles900 RPM850 - 875 RPM750 RPM700 - 725 RPM
FAQ

Frequently Asked Questions

What is motor slip? +
Slip is the difference between the rotating magnetic field speed of the stator (synchronous speed) and the actual physical rotation speed of the rotor. Without slip, no rotor current or electromagnetic torque is induced.
What is a healthy slip percentage for standard motors? +
Standard NEMA Design B induction motors typically exhibit between 2% and 5% slip at full rated mechanical load.
What does it mean if motor slip is unusually high (> 8%)? +
High slip indicates that the motor is mechanically overloaded, supply voltage is severely depressed, or rotor bars are cracked.

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