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Motor Speed Formula RPM

Motor Speed Formula:

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

Hz
poles

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1. What is the Motor Speed Formula?

Definition: This calculator determines the rotational speed (RPM) of an AC motor based on the electrical frequency and number of poles.

Purpose: It helps engineers, technicians, and electricians understand and predict motor performance characteristics.

2. How Does the Formula Work?

The formula calculates synchronous speed:

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

Where:

Explanation: The formula gives the synchronous speed - the theoretical maximum speed before slip is considered.

3. Importance of Motor Speed Calculation

Details: Knowing motor speed is crucial for proper equipment selection, performance prediction, and system design.

4. Using the Calculator

Tips: Enter the electrical frequency (typically 50 or 60 Hz) and number of poles (default 4). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is synchronous speed?
A: The theoretical speed at which the motor's magnetic field rotates, before accounting for slip.

Q2: What's a typical number of poles?
A: Common configurations are 2, 4, 6, or 8 poles, with 4 being most common for standard motors.

Q3: Why 120 in the formula?
A: It comes from converting seconds to minutes (60) and accounting for the electrical cycle (2 poles per cycle).

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

Q5: What frequency should I use?
A: Use your local power frequency - 60 Hz in North America, 50 Hz in most other countries.

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