A synchronous reluctance motor has the same structure as that of a salient pole synchronous motor except that it does not have a field winding on the rotor.
The stator has a 3-phase, symmetrical winding which creates a sinusoidal rotating field in the air gap. This causes a reluctance torque to be created on the rotor because the magnetic field induced in the rotor causes it to align with the stator field in a minimum reluctance position. The torque developed in this type of motor can be expressed as:
The reluctance torque stability limit can be seen to occur at (see figure below).
Iron laminations separated by non-magnetic materials increases reluctance flux in the qe-axis. With proper design, the reluctance motor performance can approach that of an induction motor, although it is slightly heavier and has a lower power factor. Their low cost and robustness has seen them increasingly used for low power applications, such as in fiber-spinning mills.
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