1. What is the Motor Speed Equation?

The motor speed equation calculates the rotational speed (RPM) of an AC induction motor based on the electrical frequency and the number of magnetic poles in the motor. This fundamental relationship helps in motor design and application.

2. How Does the Calculator Work?

The calculator uses the motor speed equation:

Where:

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

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

3. Importance of RPM Calculation

Details: Knowing a motor's speed is crucial for proper application matching, power calculation, and ensuring compatibility with driven equipment.

4. Using the Calculator

Tips: Enter frequency in Hz (typically 50 or 60 for mains power) and the number of poles (usually an even number like 2, 4, 6, etc.). Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why is the number 120 in the formula?
A: The 120 comes from converting seconds to minutes (60) and accounting for AC current's two alternations per cycle (2 × 60 = 120).

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

Q3: Does this apply to DC motors?
A: No, this formula is specifically for synchronous speed of AC induction motors.

Q4: What is slip in induction motors?
A: Actual RPM is slightly less than calculated due to slip (typically 2-5% less than synchronous speed).

Q5: How does voltage affect motor speed?
A: In induction motors, speed is primarily frequency-dependent. Voltage affects torque but not synchronous speed.