Poles in an Induction Motor

Replies

• 

  Vishal Sharma

  Poles are nothing but the metallic conductors around which the copper winding is done so that it acts like an electromagnet when current passes through them. The rotation of the motor is due to the magnetic field produced by these electromagnets..
  Hence, more number of poles = more speed
  
  - YouTube
  
  
  
  This video will definitely help you understanding it! 😀
• 

  CE Designer

  The reason I asked is because I was searching for a 3 hp low rpm motor and a supplier told me that the lower speed motors carry more poles than the higher speeds and are therefore more expensive. Now I am more confused 😕
  Which is it and why?
• 

  lal

  Well, actually more number of poles means lower speed. But better torque.
  
  The synchronous speed is given by, Ns = 120*f/p
  Where f is the supply frequency and p is the number of poles. Speed is inversely proportional to the number of poles.
  
  In the case of an Induction motor there is another factor called slip. The induction motor can never run at synchronous speed which is given by the above equation. If it was to run at that speed, then the rotor wouldn't cut any flux. So always an induction motor runs at a lower speed than the synchronous speed. This variation in the speed is slip.
  
  The speed at which an induction motor runs is given by Na = (synchronous speed) x (slip)
• 

  CE Designer

  lal

  Well, actually more number of poles means lower speed. But better torque.
  
  The synchronous speed is given by, Ns = 120*f/p
  Where f is the supply frequency and p is the number of poles. Speed is inversely proportional to the number of poles.
  
  In the case of an Induction motor there is another factor called slip. The induction motor can never run at synchronous speed which is given by the above equation. If it was to run at that speed, then the rotor wouldn't cut any flux. So always an induction motor runs at a lower speed than the synchronous speed. This variation in the speed is slip.
  
  The speed at which an induction motor runs is given by Na = (synchronous speed) x (slip)

  Thanks that clears things up a bit
• 

  Vishal Sharma

  I think everything is clear with that! 😀