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Motor Speed Formula:
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The motor speed equation 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 relationship is fundamental in electrical engineering and motor design.
The calculator uses the motor speed equation:
Where:
Explanation: The equation shows that motor speed is directly proportional to frequency and inversely proportional to the number of poles. The factor 120 comes from converting seconds to minutes (60) and accounting for the fact that each AC cycle creates two poles (60 × 2 = 120).
Details: Knowing a motor's speed is crucial for proper equipment selection, system design, and performance analysis. It affects torque, power output, and efficiency of motor-driven systems.
Tips: Enter the electrical frequency in Hz and the number of poles (must be an even number). Typical values are 50 or 60 Hz for frequency and 2, 4, 6, or more poles.
Q1: Why must the number of poles be even?
A: AC motors require pairs of north and south poles to function, so the number of poles is always even (2, 4, 6, etc.).
Q2: What are typical motor speeds?
A: For 60Hz systems: 3600 RPM (2-pole), 1800 RPM (4-pole), 1200 RPM (6-pole). For 50Hz systems: 3000 RPM (2-pole), 1500 RPM (4-pole), 1000 RPM (6-pole).
Q3: Does this equation work for synchronous motors?
A: Yes, this gives the synchronous speed. Actual speed of induction motors is slightly less due to slip.
Q4: How does voltage affect motor speed?
A: In induction motors, speed is primarily determined by frequency and poles, not voltage. Voltage mainly affects torque.
Q5: Can I use this for DC motors?
A: No, DC motor speed depends on different factors (voltage, current, and field strength).