1. What is the Motor Speed Formula?

The motor speed formula calculates the rotational speed of an AC induction motor based on the electrical frequency and the number of magnetic poles in the motor. This relationship is fundamental in electrical engineering and motor design.

2. How Does the Calculator Work?

The calculator uses the motor speed formula:

Where:

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

Explanation: The formula 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 motor selection, system design, and ensuring equipment operates within its designed parameters.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

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

Q2: What are typical RPM values for AC motors?
A: For 60Hz systems: 3600 RPM (2-pole), 1800 RPM (4-pole), 1200 RPM (6-pole). For 50Hz systems: 3000 RPM, 1500 RPM, 1000 RPM respectively.

Q3: Does this formula work for synchronous and induction motors?
A: This gives synchronous speed. Induction motors typically run 2-5% slower due to slip.

Q4: How does voltage affect motor speed?
A: In AC induction motors, speed is primarily determined by frequency, not voltage. Voltage affects torque but not synchronous speed.

Q5: Can this be used for DC motors?
A: No, DC motor speed depends on applied voltage and load, not on poles and frequency.