SPM stands for surface permanent magnet, a specific rotor topology for synchronous motors. In an SPM machine, the rare-earth or ferrite magnets are glued or banded directly onto the outer surface of the rotor core. This design provides high torque density and a simple magnetic circuit, but limits the motor's maximum operating speed because centrifugal forces can rip the surface-mounted magnets off the rotor.
Heard on the job
The drive faults out at high speeds because the SPM lacks the structural integrity for field-weakening operation.
Also heard as
- surface permanent magnet