1 Permanent Magnet Synchronous Motors

The Permanent Magnet Synchronous Motor (PMSM) is an AC synchronous motor driven by a three-phase controlled AC supply. The following figure shows a split view of a typical PMSM.

Figure 1-1. Split View of a PMSM Motor

The PMSM has a stationary part called the stator, a rotating part called the rotor. The stator consists of three-phase windings. When the stator is excited with a balanced three-phase voltage, it generates a rotating magnetic field. The rotor has implanted permanent magnets on its core, which generates the rotor's magnetic field. The rotor's magnetic field interacts with the stator's rotating magnetic field to produce the rotor torque.

PMSMs are broadly classified into the following two categories depending upon the rotor construction:

  • Surface-mounted PMSM (SPMSM)
  • Interior-buried PMSM (IPMSM)

The SPMSM has the permanent magnets fixed on the surface of the rotor leading to a symmetrical radial air-gap reluctance path between the rotor and the stator core. The IPMSM has the permanent magnets inserted inside the rotor core leading to a non-symmetrical radial air-gap reluctance path between the rotor and the stator core.

The following figure shows the transversal-sectional view of SPMSM and IPMSM rotor configurations.

Figure 1-2. Rotor Transversal Section