1. What is Synchronous RPM?

Synchronous RPM is the theoretical speed at which the magnetic field rotates in an AC electric motor. It's determined by 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 synchronous speed formula:

Where:

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

Explanation: The 120 factor comes from converting seconds to minutes (60) and accounting for the fact that each AC cycle produces two poles (60 × 2 = 120).

3. Importance of RPM Calculation

Details: Knowing a motor's synchronous speed helps in selecting the right motor for an application, understanding performance characteristics, and troubleshooting speed-related issues.

4. Using the Calculator

Tips: Enter frequency in Hertz (typically 50 or 60 Hz) and number of poles (always an even number - 2, 4, 6, etc.). All values must be valid (frequency > 0, poles ≥ 2).

5. Frequently Asked Questions (FAQ)

Q1: Why is actual RPM less than synchronous RPM?
A: Actual RPM is slightly less due to "slip" - the difference between synchronous speed and actual rotor speed that allows torque production.

Q2: What are typical pole numbers for motors?
A: Common configurations are 2-pole (~3600 RPM at 60Hz), 4-pole (~1800 RPM), and 6-pole (~1200 RPM).

Q3: How does frequency affect motor speed?
A: Speed is directly proportional to frequency. Doubling frequency doubles the speed (if voltage is adjusted accordingly).

Q4: Can this be used for DC motors?
A: No, DC motor speed depends on voltage and load, not poles and frequency.

Q5: What's the relationship between RPM and torque?
A: Generally, motors with lower synchronous RPM (more poles) produce higher torque at the same power rating.