1. What is the 3 Phase Motor RPM Formula?

The 3 Phase Motor RPM formula calculates the rotational speed of an AC induction motor based on the electrical supply frequency and the number of magnetic poles in the motor. This formula is fundamental in motor design and application.

2. How Does the Calculator Work?

The calculator uses the 3 phase motor RPM equation:

Where:

• \( RPM \) — Revolutions per minute
• \( f \) — Supply frequency in Hertz (Hz)
• \( p \) — Number of poles in the motor (always an even number)

Explanation: The formula derives from the relationship between electrical frequency and mechanical rotation in AC induction motors. The factor of 120 comes from converting seconds to minutes (60) and accounting for the phase relationship (2).

3. Importance of RPM Calculation

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

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: Why is the number of poles always even?
A: AC motors require pairs of north and south magnetic poles, so the total number is always even.

Q2: What is synchronous speed vs actual speed?
A: This formula gives synchronous speed. Actual speed is slightly less due to slip (typically 2-5% less for induction motors).

Q3: What RPM can I expect from a 4-pole motor at 60Hz?
A: 1800 RPM (synchronous speed), with actual speed around 1725-1750 RPM accounting for slip.

Q4: How does voltage affect RPM?
A: Voltage doesn't directly affect RPM in induction motors. RPM is primarily determined by frequency and poles.

Q5: Can I use this for single-phase motors?
A: The formula works similarly, but single-phase motors often have additional design considerations affecting speed.