FAQ

Motion Control

Frequency Inverters

Servomotors / Servo Drivers

Frequency Inverter Topic: Calculate Rotational Speed of an Induction Motor

FAQ No. FAQ02018

Question

We are using an Inverter for speed control. How can we calculate the rotational speed of an induction motor?
 

Answer

Generally, the speed (N) of an induction motor is expressed by the following formula:

N = (120f/P) × (1 - S) (rpm)
f: Primary frequency
P: Number of motor poles
S: Slip

Example:

Where f = 60 Hz, P = 4 poles, and S = 3%,
N = ( (120 × 60) ⁄ 4) × (1 − 0.03) = 1,746 (rpm)
 

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