Difference between switched reluctance motor and synchronous reluctance motor in points
Answers
1. PMSM
Permanent Magnet Synchronous Machines (PMSM) have of course permanent magnets in their rotor. They are compact, powerful and offer excellent dynamic response. Permanent magnets are expensive and with abuse (overheating or overcurrent) can be partially demagnetized. As we will see later pure PMSM machines are uncommon.
2. SynRM
Synchronous Reluctance Machines (SynRM) have a rotor made of layers of magnetically soft material. These ferromagnetic layers orient along the stator magnetic field and follow it as it rotates.
(illustration by ABB)
SynRM have a cost advantage as they do not need expensive rare earth elements. They tolerate abuse well, as there are no magnets to overheat and demagnetize. Certain designs can also offer advantages at higher speeds (no field weakening). They generally have lower starting torque and poorer power to weight ratio than PMSM. Some sources claim SynRM are more nonlinear and harder to control.
SynRM also successfully compete with induction motors for variable speed fan and pump drives (lower size, lower losses especially at partial load and cooler rotor resulting in longer bearing life).
3. Best of both worlds
The so called internal magnet (IPM) or burried magnet motors combine both permanent magnet and reluctance torque in one machine. This offers significant flexibility in the motor design. This is the type used in many electric/hybrid cars.
Another hybrid design is the Permanent Magnet-Assisted Synchronous Reluctance Motor (PMa-SynRM).
The basic differences between switched (SRM) and synchronous (SynRM) reluctance machines were covered: SRMs can be noisy and hard to supply. SRMs have robust rotors. The number of rotor poles is closely tied to the number of stator teeth in an SRM.