1. What is the RPM Formula for Motors?

The RPM (Revolutions Per Minute) formula calculates the rotational speed of an AC 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 RPM 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

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 RPM is essential for proper motor selection, performance analysis, and ensuring compatibility with driven equipment. It affects torque, power output, and efficiency.

4. Using the Calculator

Tips: Enter the power supply frequency in Hz and the number of poles in the motor. Standard power frequencies are 50Hz or 60Hz. Pole numbers are typically even (2, 4, 6, etc.).

5. Frequently Asked Questions (FAQ)

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

Q2: Does this formula work for all motor types?
A: This applies specifically to synchronous AC motors. Induction motors run slightly slower due to slip.

Q3: What are typical RPM values for motors?
A: Common values include 3600 RPM (2-pole at 60Hz), 1800 RPM (4-pole at 60Hz), and 1500 RPM (4-pole at 50Hz).

Q4: How does voltage affect RPM?
A: Voltage doesn't directly affect RPM in AC motors - speed is primarily determined by frequency and poles.

Q5: Can I use this for DC motors?
A: No, DC motor speed depends on voltage and load, not frequency and poles.