1. What is the Motor RPM Formula?

The Motor RPM formula calculates the rotational speed of an AC motor based on the frequency of the power supply and the number of magnetic poles in the motor. This fundamental equation is essential for motor design, selection, and performance analysis.

2. How Does the Calculator Work?

The calculator uses the motor RPM formula:

Where:

• \( RPM \) — Rotational speed in revolutions per minute
• \( Freq \) — Frequency of the power supply in Hertz (Hz)
• \( Poles \) — Number of magnetic poles in the motor

Explanation: The formula calculates the synchronous speed of an AC motor, which is the theoretical maximum speed the motor can achieve without slip.

3. Importance of RPM Calculation

Details: Accurate RPM calculation is crucial for motor selection, performance prediction, system design, and ensuring compatibility with driven equipment requirements.

4. Using the Calculator

Tips: Enter frequency in Hz and the number of poles. Both values must be positive numbers (frequency > 0, poles ≥ 2 and typically even numbers).

5. Frequently Asked Questions (FAQ)

Q1: What is synchronous speed?
A: Synchronous speed is the theoretical speed at which the motor's magnetic field rotates. Actual motor speed is slightly less due to slip.

Q2: Why is the constant 120 used in the formula?
A: The constant 120 comes from converting seconds to minutes (60) and accounting for the fact that each AC cycle produces two magnetic poles (×2).

Q3: What are typical pole numbers for AC motors?
A: Common pole configurations are 2, 4, 6, 8 poles, with corresponding synchronous speeds of 3600, 1800, 1200, and 900 RPM at 60 Hz.

Q4: How does slip affect actual motor speed?
A: Actual motor speed is typically 2-5% less than synchronous speed due to slip, which allows the motor to produce torque.

Q5: Can this formula be used for DC motors?
A: No, this formula applies only to AC synchronous and induction motors. DC motor speed depends on voltage and field strength.