Motor speeds according to poles

[cscmd]

I was looking for a table of speeds of 3 phase motors according to no of poles for 50Hz. Does anyone know the whereabouts of one of these?

 

[EnglishMuffin]

n = f/p

where n = rpm
f = frequency - cpm
p = number of pairs of poles

So :

2 poles - 3000 rpm
4 poles - 1500 rpm
8 poles - 750 rpm etc

(synchronous speeds - ie not counting slip)

 

[electricpete]

agreed.

Although the f in the numerator has not been clearly defined.

I would prefer to say sync speed = 2*FL / poles
where FL is line frequency.

Put the units in and you'll see the need for any additional required unit conversions such as 60rpm / hz.

Actual speed for general purpose NEMA design B motor is required to be in the range 0-5% below sync speed, and usually in the range 0-1% below sync speed.