This tool converts Motor Frequency (Hz) to Revolutions per Minute (RPM)
Calculator
Enter
- Motor Frequency in Hz
- Number of poles
Formula
RPM = 120 × f/p
Where:
- f is the frequency in hertz (Hz).
- p is the number of poles the motor has.
- 120 is a constant used to convert the frequency and number of poles into revolutions per minute.
The factor 120 comes from 60 seconds per minute multiplied by 2, accounting for the fact that each cycle of an AC motor requires two poles (a north and a south).
Example Calculation
Use the tool on this page to calculate the RPM of an AC motor given a frequency of 50 Hz and a motor with 4 poles. It gives an answer of 1500 RPM.
What is Motor Frequency?
Motor frequency, often referred to in terms of the electrical input frequency supplied to the motor, significantly affects the motor’s speed. This frequency is usually measured in hertz (Hz) and is directly related to the voltage frequency supplied from the power source.
Why Convert Frequency to RPM?
For AC motors, particularly those that operate under variable frequency drives (VFDs), adjusting the frequency of the electrical supply can control the speed of the motor. Knowing the exact RPM at which a motor operates based on a given frequency is essential for:
- Optimizing Performance: Ensuring the motor operates efficiently under different load conditions.
- Preventing Damage: Avoiding speeds that may harm the motor due to mechanical resonances or exceeding the motor’s design specifications.
- Control and Automation: Precisely controlling the speed of motors in automated systems to synchronize with other components.