Calculating Poles in a 3-Phase Induction Motor

[rictor]

how many poles does 3 phase, 60 hertz induction motor which runs at 715 r/min at no load and at 670 r/min at full load have and how is it calculated?

 

[CWatters]

From..

http://www.precision-elec.com/faq-vfd-how-do-i-calculate-rpm-for-three-phase-induction-motors/

RPM = (120 * Freq) /N
where N = Number of poles
So
N = (120 * Freq)/715
= (120 * 60)/715
= 10

Edit: Actually 10 poles gives 720 rpm.

The slip % is
((Synchronous Speed – Rated Full Load Speed) / (Synchronous Speed)) * 100%
(715-670)*100/715 = 6.3%