motor poles

[jrb5879]

What is the formula to figure how many poles in a motor?

 

[electricpete]

p = 2 LF / N
where p is number of poles
LF is line frequency
N is syncrounous speed (slightly higher than nameplate speed for induction motor).

If LF is in hz then N must be in rev per second. Otherwise add conversions seconds to minutes.

 

[jbartos]

Suggestion: Reference:
Gordon R. Slemon "Magnetolectric Devices Transducers, Transformers, and Machines," John Wiley and Sons, Inc., 1966,
page 372:

P= 2 x ws x (1-s)/n
where
P = number of motor poles, in poles
ws = 2 x pi x fs, in rad/sec synchronous angular speed
fs = synchronous frequency in Hz
s = slip, in per unit
n = rotor speed in rad/sec, (p-pole motor rotor speed)