1. What is Motor RPM?

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

2. How Does the Calculator Work?

The calculator uses the synchronous speed formula:

Where:

• \( RPM \) — Revolutions per minute
• \( f \) — Electrical frequency in Hertz (Hz)
• \( p \) — Number of magnetic poles in the motor

Explanation: The formula calculates the synchronous speed of an AC motor, where the rotor speed matches the rotating magnetic field speed.

3. Importance of RPM Calculation

Details: Knowing a motor's RPM is essential for proper system design, ensuring compatibility with driven equipment, and achieving desired performance in applications like pumps, fans, and conveyors.

4. Using the Calculator

Tips:

• Enter frequency in Hz (typically 50 or 60 Hz for mains power)
• Poles must be an even number (2, 4, 6, etc.)
• For induction motors, actual RPM will be slightly less than calculated (slip)

5. Frequently Asked Questions (FAQ)

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

Q2: What's the difference between synchronous and actual RPM?
A: Synchronous speed is theoretical. Actual RPM is slightly lower due to slip (especially in induction motors).

Q3: How do I determine the number of poles in a motor?
A: Check motor nameplate or specifications. Common configurations are 2-pole (high speed) or 4-pole (medium speed).

Q4: What RPM should I expect for a 60Hz, 4-pole motor?
A: (120 × 60)/4 = 1800 RPM synchronous speed (actual ~1750 RPM with slip).

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