Induction Motor Speed Formula

Induction Motor Speed Formula:

\[ n_s = \frac{120 \times f}{p} \]

Synchronous Speed (n_s):

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1. What is the Induction Motor Speed Formula?

The Induction Motor Speed Formula calculates the synchronous speed of an AC induction motor based on the supply frequency and number of poles. This represents the rotational speed of the magnetic field in the stator.

2. How Does the Calculator Work?

The calculator uses the synchronous speed formula:

\[ n_s = \frac{120 \times f}{p} \]

Where:

\( n_s \) — Synchronous speed (revolutions per minute)
\( f \) — Supply frequency (Hertz)
\( p \) — Number of poles (must be even number)

Explanation: The formula calculates the speed at which the magnetic field rotates in the stator. The actual rotor speed is slightly less than synchronous speed due to slip.

3. Importance of Synchronous Speed Calculation

Details: Knowing the synchronous speed is essential for motor selection, speed control applications, and understanding motor performance characteristics in various industrial applications.

4. Using the Calculator

Tips: Enter frequency in Hz and number of poles (must be even number, typically 2, 4, 6, 8, etc.). All values must be valid (frequency > 0, poles ≥ 2 and even).

5. Frequently Asked Questions (FAQ)

Q1: What is synchronous speed vs actual speed?
A: Synchronous speed is the speed of the magnetic field, while actual rotor speed is slightly less due to slip (typically 2-5% less for induction motors).

Q2: Why must the number of poles be even?
A: Poles always come in pairs (north and south) in AC motors, so the pole count must be an even number for proper magnetic field formation.

Q3: What are typical synchronous speeds?
A: For 60 Hz systems: 3600 RPM (2-pole), 1800 RPM (4-pole), 1200 RPM (6-pole). For 50 Hz systems: 3000 RPM (2-pole), 1500 RPM (4-pole), 1000 RPM (6-pole).

Q4: Can this formula be used for synchronous motors?
A: Yes, for synchronous motors, the rotor actually runs at synchronous speed, while induction motors run slightly slower due to slip.

Q5: How does voltage affect motor speed?
A: In induction motors, speed is primarily determined by frequency and poles, not voltage. Voltage affects torque but has minimal effect on synchronous speed.