VFD and Motor Speed Relationship

The motor speed (RPM) can be calculated using a Variable Frequency Drive (VFD) by adjusting the frequency supplied to the motor. The formula to calculate the motor speed is as follows:

Motor Speed (RPM) = \( \frac{120 \times \text{Frequency (Hz)}}{\text{Number of Poles}} \)

Frequency (Hz):

Frequency is the electrical frequency that powers the motor. The VFD adjusts this frequency to control the speed of the motor.

Number of Poles:

The number of poles in the motor determines the relationship between electrical frequency and mechanical speed. More poles result in a lower RPM.

Example Calculation

If the input frequency is 60 Hz and the motor has 4 poles, the motor speed would be:

Motor Speed (RPM) = \( \frac{120 \times 60}{4} = 1800 \, \text{RPM} \)