1. What is the RPM Formula?

The RPM (Revolutions Per Minute) formula calculates the rotational speed of an AC motor based on the electrical frequency and the number of magnetic poles in the motor. It's fundamental for understanding motor performance and selecting the right motor for applications.

2. How Does the Calculator Work?

The calculator uses the RPM formula:

Where:

• \( f \) — Electrical frequency in Hertz (Hz)
• \( p \) — Number of magnetic poles in the motor
• 120 — Constant factor (60 seconds × 2 for alternating current)

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

3. Importance of RPM Calculation

Details: Knowing a motor's RPM is crucial for proper motor selection, speed control, and ensuring compatibility with driven equipment. It affects torque, power output, and overall system performance.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: Why does the number of poles affect RPM?
A: More poles create more magnetic cycles per revolution, resulting in slower rotation for the same frequency.

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), etc.

Q3: Does this apply to DC motors?
A: No, this formula is specific to synchronous AC motors. DC motor speed depends on voltage and load.

Q4: What is synchronous vs actual RPM?
A: This calculates synchronous speed. Actual speed is slightly less due to slip in induction motors.

Q5: How does frequency affect motor speed?
A: Higher frequency increases speed proportionally. Variable frequency drives use this principle for speed control.