1. What is VFD Frequency to RPM Calculation?

The VFD (Variable Frequency Drive) frequency to RPM calculation determines the rotational speed of an AC motor based on the frequency supplied by the VFD and the number of motor poles. This is essential for motor control and speed regulation in industrial applications.

2. How Does the Calculator Work?

The calculator uses the RPM formula:

Where:

• \( RPM \) — Rotational speed in revolutions per minute
• \( Hz \) — Frequency in hertz
• \( Poles \) — Number of motor poles (must be even number)

Explanation: The formula calculates the synchronous speed of an AC motor, where 120 represents the conversion factor (60 seconds × 2 for AC cycle).

3. Importance of RPM Calculation

Details: Accurate RPM calculation is crucial for motor selection, speed control, process optimization, and preventing motor damage from operating outside designed speed ranges.

4. Using the Calculator

Tips: Enter frequency in Hz and number of poles (must be even number ≥ 2). Common pole configurations are 2, 4, 6, or 8 poles for most industrial motors.

5. Frequently Asked Questions (FAQ)

Q1: What is the relationship between frequency and RPM?
A: RPM is directly proportional to frequency - doubling the frequency doubles the motor speed, assuming constant pole count.

Q2: Why must poles be an even number?
A: AC motors require even numbers of poles to create the rotating magnetic field necessary for operation.

Q3: Is this synchronous or actual RPM?
A: This calculates synchronous speed. Actual RPM will be slightly less due to slip in induction motors.

Q4: What are typical motor speeds?
A: At 60Hz: 2-pole = 3600 RPM, 4-pole = 1800 RPM, 6-pole = 1200 RPM, 8-pole = 900 RPM (synchronous speeds).

Q5: Can VFDs operate above motor rated frequency?
A: Yes, but motor torque capability decreases proportionally with frequency increase above rated frequency.