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Motor Frequency Formula:
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Motor frequency refers to the synchronous speed frequency of an AC motor, which is determined by the rotational speed and number of magnetic poles. It represents the electrical frequency at which the motor operates to achieve synchronous speed.
The calculator uses the motor frequency formula:
Where:
Explanation: The formula calculates the synchronous frequency required for an AC motor to operate at a specific rotational speed with a given number of poles. The constant 120 converts minutes to seconds and accounts for the electrical cycle relationship.
Details: Accurate frequency calculation is crucial for motor selection, speed control applications, variable frequency drive (VFD) programming, and ensuring motors operate within their designed specifications for optimal performance and efficiency.
Tips: Enter RPM (rotational speed) in revolutions per minute and the number of poles in the motor. Both values must be positive numbers (RPM > 0, Poles ≥ 2 and typically even numbers).
Q1: What is synchronous speed in AC motors?
A: Synchronous speed is the speed at which the magnetic field rotates in the stator, determined by the supply frequency and number of poles.
Q2: Why is the number 120 used in the formula?
A: The constant 120 comes from converting minutes to seconds (60) and accounting for the fact that each electrical cycle corresponds to two pole passes (×2).
Q3: What are typical pole numbers for AC motors?
A: Common pole numbers are 2, 4, 6, 8, or 12 poles, with 2-pole motors having the highest speed and more poles providing lower speeds.
Q4: How does frequency affect motor speed?
A: For AC induction motors, speed is directly proportional to frequency. Increasing frequency increases speed, while decreasing frequency reduces speed.
Q5: Can this formula be used for all motor types?
A: This formula is primarily for AC synchronous motors. Induction motors typically operate at slightly lower speeds (slip speed) than the calculated synchronous speed.