3-phase motor RPM=fx60/p

[gazdkw82]

just going through some mock exams to prepare me for the 202 exam I have next week.

Came across the following question

A 3-phase synchronous motor is required to operate on a 50Hz supply and run at 500 rpm. The number of poles required is:

So I know the formula for this as

RPM = Fx60/poles

Therefore poles = RPMxF/60

I can't seem to get the right answer here. I'm sure it's something to do with my transposition?? Any help would be appreciated

 

[Leesparkykent]

(Fx60)/RPM will give you the number of pole pairs

So times the number of pole pairs to get the number of poles.

50x60=3000

3000/500=6 pole pairs

pairsx2=12 poles

IIRC...I'm sure someone more knowledgeable on the matter will correct me if I'm wrong.
@telectrix