Frequency versus motor RPM and number of poles

[DunceKirchhoff]

Which equation is correct I have seen both-

F=N/60*P
Or
F=N/120*P

This is Frequency, N=RPM P=Poles

 

[jedishrfu]

This website has some discussion on the equation and may help:

http://www.allinterview.com/showanswers/153216.html

 

[DunceKirchhoff]

Thanks that helped!

 

[jedishrfu]

Don't forget to use the Thanks button and also PF is conducting PF member award voting here:

https://www.physicsforums.com/forumdisplay.php?f=233

 

[HalfLostAndSearching]

I would first clarify that the equation given is for calculating the frequency of an AC motor, where F represents frequency, N represents motor RPM, and P represents the number of poles. The correct equation to use depends on the type of motor being considered.

If the motor is a synchronous motor, which has a rotating magnetic field that moves at a constant speed with respect to the stator, then the correct equation is F=N/120*P. This is because the frequency of a synchronous motor is directly proportional to the number of poles and the motor RPM.

On the other hand, if the motor is an induction motor, which has a rotating magnetic field that moves at a speed slightly lower than the stator's speed, then the correct equation is F=N/60*P. This is because the frequency of an induction motor is half of the synchronous motor's frequency, and the motor RPM and number of poles still have a direct relationship.

Overall, both equations are correct, but they are applicable to different types of motors. It is important to understand the type of motor being used and use the appropriate equation to accurately calculate the frequency.