1. What is Motor Speed (RPM)?

Motor speed, measured in revolutions per minute (RPM), indicates how fast the motor's shaft rotates. The RPM depends 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:

• \( RPM \) — Revolutions per minute
• \( f \) — Frequency of power supply (Hz)
• \( p \) — Number of magnetic poles in the motor

Explanation: The formula shows that RPM is directly proportional to frequency and inversely proportional to the number of poles. The constant 120 comes from converting seconds to minutes (60) and accounting for alternating current cycles (2).

3. Importance of RPM Calculation

Details: Knowing a motor's RPM is crucial for proper equipment selection, performance evaluation, and ensuring compatibility with mechanical systems. It affects torque, power output, and efficiency.

4. Using the Calculator

Tips: Enter frequency in Hertz (Hz) and number of poles (must be an even number). Common pole numbers are 2, 4, 6, etc. For 60Hz power, typical RPM values are 3600 (2-pole), 1800 (4-pole), 1200 (6-pole).

5. Frequently Asked Questions (FAQ)

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

Q2: What's the difference between synchronous and actual RPM?
A: This formula calculates synchronous speed. Actual RPM is slightly less due to slip (typically 2-5% less for induction motors).

Q3: How does voltage affect RPM?
A: Voltage doesn't directly affect synchronous RPM, but insufficient voltage may prevent a motor from reaching its rated speed.

Q4: Can I use this for DC motors?
A: No, this formula is for AC synchronous motors. DC motor speed depends on voltage and load.

Q5: What if my motor has variable frequency?
A: For VFD-controlled motors, use the current output frequency from the drive in the calculation.