1. What is the Electric Motor Speed Formula?

The electric motor speed formula calculates the rotational speed of an AC induction motor based on the frequency of the power supply and the number of magnetic poles in the motor. This relationship is fundamental in electrical engineering and motor design.

2. How Does the Calculator Work?

The calculator uses the electric motor speed formula:

Where:

• \( RPM \) — Rotational speed in revolutions per minute
• \( f \) — Frequency of the power supply in Hertz (Hz)
• \( p \) — Number of magnetic poles in the motor (always an even number)

Explanation: The formula shows that motor speed is directly proportional to frequency and inversely proportional to the number of poles.

3. Importance of RPM Calculation

Details: Knowing a motor's speed is crucial for proper application selection, performance prediction, and system design in industrial and commercial settings.

4. Using the Calculator

Tips: Enter frequency in Hz and number of poles (must be even). Typical values are 50 or 60 Hz for frequency and 2, 4, 6, etc. for poles.

5. Frequently Asked Questions (FAQ)

Q1: Why is the number 120 used in the formula?
A: The factor 120 comes from converting seconds to minutes (60) and accounting for the fact that each AC cycle produces two poles (60 × 2 = 120).

Q2: What are typical RPM values for AC motors?
A: Common values are 3600 RPM (2-pole at 60Hz), 1800 RPM (4-pole), 1200 RPM (6-pole), and 900 RPM (8-pole).

Q3: Does this formula work for DC motors?
A: No, this formula is specific to AC induction motors. DC motor speed depends on voltage and other factors.

Q4: Why must the number of poles be even?
A: Magnetic poles always come in north-south pairs, so the total number must be even.

Q5: What is slip in motor speed?
A: Actual speed is slightly less than synchronous speed (calculated here) due to slip, which allows torque production.