1. What is the AC Motor Speed Formula?

The AC motor speed formula calculates the rotational speed of an alternating current (AC) motor based on the frequency of the power supply and the number of magnetic poles in the motor. This is fundamental for understanding motor performance in various applications.

2. How Does the Calculator Work?

The calculator uses the AC motor speed equation:

Where:

• \( RPM \) — Revolutions per minute (motor speed)
• \( f \) — Frequency of the power supply in Hertz (Hz)
• \( p \) — Number of magnetic poles in the motor (always an even number)

Explanation: The 120 factor comes from converting seconds to minutes (60) and accounting for the alternating nature of AC power (2 poles per cycle). The speed is inversely proportional to the number of poles.

3. Importance of Motor Speed Calculation

Details: Knowing the synchronous speed of an AC motor is crucial for selecting the right motor for an application, understanding performance characteristics, and troubleshooting speed-related issues in motor operation.

4. Using the Calculator

Tips: Enter the power supply frequency in Hz and the number of poles in the motor (must be an even number). Common pole numbers are 2, 4, 6, or 8 for most industrial motors.

5. Frequently Asked Questions (FAQ)

Q1: Is this the actual or synchronous speed?
A: This calculates synchronous speed. Actual speed is slightly less due to slip in induction motors.

Q2: Why must pole number be even?
A: AC motors require pairs of north and south poles, so the total number is always even.

Q3: What's the speed at 50Hz vs 60Hz?
A: For a 4-pole motor: 1500 RPM at 50Hz, 1800 RPM at 60Hz. This is why equipment may run faster in 60Hz countries.

Q4: Can I use this for DC motors?
A: No, DC motor speed depends on voltage and is not determined by this pole/frequency relationship.

Q5: How does load affect actual speed?
A: In induction motors, speed decreases slightly with increasing load (typically 2-5% slip at full load).