1. What is Motor RPM?

RPM (Revolutions Per Minute) measures how many complete rotations a motor makes in one minute. It's a critical parameter for motor selection and application in various mechanical systems.

2. How Does the Calculator Work?

The calculator uses the RPM equation:

Where:

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

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

3. Importance of RPM Calculation

Details: Knowing a motor's RPM is essential for proper system design, ensuring compatibility with driven equipment, and selecting appropriate gear ratios or pulleys.

4. Using the Calculator

Tips: Enter frequency in Hz (typically 50 or 60 Hz for mains power) and number of poles (always an even number, e.g., 2, 4, 6, etc.). All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: Why does RPM decrease with more poles?
A: More poles create more magnetic cycles per revolution, causing the motor to rotate slower at the same frequency.

Q2: What are typical RPM values for AC motors?
A: For 60Hz systems: 3600 RPM (2-pole), 1800 RPM (4-pole), 1200 RPM (6-pole). For 50Hz systems: 3000 RPM, 1500 RPM, 1000 RPM respectively.

Q3: Is this formula accurate for all motor types?
A: This gives synchronous speed for AC induction motors. Actual speed will be slightly less due to slip (typically 2-5%).

Q4: How does voltage affect RPM?
A: Voltage doesn't directly affect synchronous RPM, but insufficient voltage may prevent the motor from reaching its designed speed.

Q5: Can I use this for DC motors?
A: No, DC motor speed depends on voltage and load. This formula only applies to AC synchronous motors.