Motor Frequency to RPM Calculator

RPM Formula:

\[ RPM = \frac{120 \times f}{p} \]

RPM (Revolutions Per Minute):

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1. What is the Frequency to RPM Calculation?

The RPM (Revolutions Per Minute) calculation from frequency is a fundamental formula in electrical engineering that determines the rotational speed of an AC induction motor based on the power supply frequency and the number of magnetic poles in the motor.

2. How Does the Calculator Work?

The calculator uses the standard RPM formula:

\[ RPM = \frac{120 \times f}{p} \]

Where:

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

Explanation: The formula derives from the relationship between the alternating current frequency and the rotating magnetic field in the motor. The 120 factor comes from converting seconds to minutes (60) and accounting for the fact that each AC cycle produces two poles (×2).

3. Importance of RPM Calculation

Details: Knowing a motor's RPM is crucial for proper motor selection, system design, and performance evaluation. It affects torque, power output, and compatibility with driven equipment.

4. Using the Calculator

Tips: Enter the power supply frequency in Hz (typically 50 or 60 Hz for mains power) and the number of poles in the motor (common values are 2, 4, 6, or 8 poles). The number of poles must be an even number.

5. Frequently Asked Questions (FAQ)

Q1: Why is the number of poles always even?
A: AC motors require pairs of magnetic poles (north and south) to create the rotating magnetic field, so the pole count is always an even number.

Q2: What's the RPM for a standard 4-pole motor at 60Hz?
A: (120 × 60) / 4 = 1800 RPM (this is the synchronous speed; actual speed will be slightly less due to slip).

Q3: Does this formula work for all motor types?
A: This formula calculates synchronous speed for AC induction motors. It doesn't apply to DC motors or synchronous motors operating at exactly synchronous speed.

Q4: Why is actual RPM less than calculated RPM?
A: The formula gives synchronous speed. Actual speed is slightly less due to "slip" which allows torque production in induction motors.

Q5: How does voltage affect RPM?
A: Voltage doesn't directly affect RPM in AC induction motors. RPM is primarily determined by frequency and pole count, while voltage affects torque capability.