Induction machine-1

Hi folks.

Let us talk about most common misconception that we people have.  If I say, I have a 6 pole induction machine what does it mean?

1      I have a machine with 6 poles per phase and total no of poles after energizing the winding will be 6*3 phases = 18

2    I have 6 poles in total. So it must be 2 poles per phase and 2*3= 6 (total poles)

Well. Actually both the above answers are wrong.

When I say a 6 pole induction machines it by default means that there are 6 poles in the machine per phase. But the total no of poles in the machine is not 18. It is 6 only. 

When we excite the winding of this machine, we get 6 poles in the space around rotor symmetrically distributed in space. And they belong to different phases at different instant of time. So there are 6 poles in the space in total. But while stating the rating of the machine we state it as 6 poles ‘per phase’ only.

I know it’s a bit confusing but if you draw 3 winding at 120 degree spatially displaced and pass 3 phases then it is quite clear that the 2 poles are resultant of the individual magnetic field produced. The total no of poles is 2 per phase as we have already stated and one of the poles (that are rotating, say N) belongs to the phase carrying positive maximum and other pole (say S) is the resultant of the remaining two phases that are on half of the negative maximum.

Thank you for your time and please feel free to  leave comment about any doubts and suggestions.