Patent ID: 7944164

Claim:
A method of determining rotor position in a PMSM having a permanent magnet rotor producing a magnetic flux having a magnet direction, the permanent magnet rotor rotatable within stator coils receiving an electric signal to generate a stator field, the method comprising the steps of: (a) in a first period, applying a first electrical signal to the stator coils to create a rotating stator field having a rotational speed and strength insufficient to cause a movement of the rotor; (b) monitoring current flow through the stator during (a) to detect a fluctuation in current caused by anisotropic saliency of the permanent magnet rotor to deduce a magnetization axis; (c) in a second period after the first period, applying a second electrical signal to the stator coils to produce a magnetic field aligned with the magnetization axis to minimize rotor motion; and (d) analyzing current flow through the stator during the second period to deduce the direction of the magnetic flux and thus an orientation of the rotor.