Reluctance Motor
 The origin of this motor can be traced back to 1842. The 
 Synchronous reluctance motor has a stator wounded as that 
 of a 3-phase induction machine. It works as a synchronous 
 motor without DC field winding in its rotor.
 A reluctance motor is a type of electric motor that induces 
 non-permanent magnetic poles on the ferromagnetic rotor. 
 Torque is generated through the phenomenon of magnetic 
 reluctance.  Hence,  it  is  not  a  permanent  magnet  motor, 
 because its salient rotor is composed of soft ferromagnetic 
 material (of a thin hysteresis loop with high remanence and 
 small coercive force).
  Construction of Reluctance Motor Rotor
   1- Notch-Type Rotor
  • “Notch” areas are of 
    “High-Reluctance”
  • “Pole” areas are known as 
    “Salient” Poles
     • Number of salient poles 
      must match the number 
      of stator poles
                                    Figure (2)
   2- Flat and Barrier Slot Rotors
                  Figure (4)
   Principle of Operation
   When  a  piece  of  magnetic 
   material is free to move in a 
   magnetic  field,  it  will  align 
   itself  with  the  magnetic  field 
   to minimize the reluctance  of 
   the magnetic circuit. To put it 
   another  way  the  piece  will 
   orient   itself   towards     the 
   magnetic  pole  creating  the 
   field. The torque on the rotor 
   created  in  this  way  is  called 
   the reluctance torque.                          Figure (5)
  • Rotor accelerates towards synchronous 
    speed
  • At   a   “critical”   speed,   the    low-
    reluctance paths provided by the salient 
    poles  will  cause  them  to  “snap”  into 
    synchronism with the rotating flux.
  • When  the  rotor  synchronizes,  slip  is 
    equal to zero
  • Rotor  pulled  around  by  “reluctance 
    torque”
  • Figure     (6)     shows      the    rotor 
                                                       Figure (6)
    synchronized at no load.