1. What is the RPM Formula?

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.

2. How Does the Calculator Work?

The calculator uses the RPM formula:

Where:

• \( f \) — Frequency of the power supply (Hz)
• \( p \) — Number of magnetic poles in the motor
• 120 — Constant factor (60 seconds × 2 poles)

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

3. Importance of RPM Calculation

Details: Knowing a motor's RPM is essential for proper equipment selection, performance analysis, and ensuring compatibility with driven machinery.

4. Using the Calculator

Tips: Enter frequency in Hz (typically 50 or 60 Hz) and the number of poles (always an even number, typically 2, 4, 6, or 8). All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: Why is the number of poles always even?
A: AC motors require pairs of north and south magnetic poles, so the number is always even (2, 4, 6, etc.).

Q2: What is synchronous speed?
A: This formula calculates synchronous speed - the theoretical maximum speed. Actual speed is slightly less due to slip.

Q3: How does frequency affect motor speed?
A: Higher frequency increases RPM proportionally. A 60Hz motor runs 20% faster than a 50Hz motor with the same poles.

Q4: What are typical RPM values?
A: Common values are 3600 RPM (2-pole at 60Hz), 1800 RPM (4-pole), 1200 RPM (6-pole), and 900 RPM (8-pole).

Q5: Can this be used for DC motors?
A: No, this formula is for AC induction motors only. DC motor speed depends on voltage and load.