Motor Hz to RPM Calculator
Accurate motor speed calculations for AC induction motors
Motor Hz to RPM Calculator
Compliant with NEMA and IEC Standards
Results:
Synchronous RPM: 0.00
Approx. Actual RPM (3% Slip): 0.00
How to Use the Calculator
Input Frequency
- Enter the electrical frequency in Hertz (Hz).
- Common frequencies are 50 Hz or 60 Hz.
Input Number of Poles
- Enter the number of poles of the motor.
- Poles must be an even number (e.g., 2, 4, 6, 8).
View Results
- The calculator will display the Synchronous RPM.
- It also provides an approximate Actual RPM, considering a typical slip.
Motor Speed Fundamentals
Synchronous Speed
Synchronous speed is the speed of the rotating magnetic field in an AC motor. It depends on the frequency of the power supply and the number of poles in the motor.
- Determined by frequency and poles
- Ideal speed without load
Actual Speed & Slip
- Actual speed is always less than synchronous speed.
- The difference is called "slip," typically 2-5% for induction motors.
- Slip is necessary for torque production.
Key Formulas:
Synchronous RPM = (Frequency × 120) / Number of Poles
Actual RPM = Synchronous RPM × (1 - Slip)
Calculation Formulas
Synchronous RPM:
Ns = (f × 120) / P
Actual RPM:
Nr = Ns × (1 - s)
Where: Ns = Synchronous RPM, f = Frequency (Hz), P = Number of Poles, Nr = Actual RPM, s = Slip (decimal)
Example Calculation
For a 4-pole motor at 60 Hz:
Frequency (f): 60 Hz
Poles (P): 4
Synchronous RPM = (60 × 120) / 4 = 1800 RPM
Assuming 3% slip (0.03):
Actual RPM = 1800 × (1 - 0.03) = 1800 × 0.97 = 1746 RPM
Synchronous RPM = 1800.00 | Approx. Actual RPM = 1746.00
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