Home
Back
RPM Formula:
| From: | To: |
Motor RPM (Revolutions Per Minute) refers to the rotational speed of an AC motor's shaft. The synchronous speed is determined by the frequency of the power supply and the number of magnetic poles in the motor design.
The calculator uses the synchronous speed formula:
Where:
Explanation: This formula calculates the synchronous speed of an AC induction motor, which is the theoretical maximum speed the motor can achieve without slip.
Details: Knowing the motor RPM is essential for proper motor selection, application matching, speed control, and understanding the motor's performance characteristics in various industrial and commercial applications.
Tips: Enter the power supply frequency in Hz and the number of poles in the motor. Common frequencies are 50 Hz or 60 Hz depending on your region. Number of poles is typically 2, 4, 6, or 8 for most industrial motors.
Q1: What is synchronous speed vs actual speed?
A: Synchronous speed is the theoretical maximum speed, while actual speed is slightly lower due to slip in induction motors. The difference is typically 2-5% for most applications.
Q2: Why is the constant 120 used in the formula?
A: The constant 120 comes from converting seconds to minutes (60) and accounting for the fact that each AC cycle produces two magnetic poles (×2), so 60 × 2 = 120.
Q3: What are common pole configurations?
A: Common configurations include 2-pole (3600 RPM at 60 Hz), 4-pole (1800 RPM at 60 Hz), 6-pole (1200 RPM at 60 Hz), and 8-pole (900 RPM at 60 Hz).
Q4: Does this work for DC motors?
A: No, this formula is specific to AC induction motors. DC motor speed is controlled by voltage and load characteristics.
Q5: How does frequency affect motor speed?
A: Motor speed is directly proportional to frequency. Doubling the frequency doubles the synchronous speed, within the motor's design limits.