Device for determining angular position of e.g. rotor shaft, connected to fan of electric motor, has magnetizing device alternatively arranged on each track, so that south polar region follows north polar region

摘要

The device has a magnetic region i.e. pole disc (6), mounted at a side of a fan wheel (4), where the side of the fan wheel is arranged behind a conductor plate (5). A set of sensors is arranged on the conductor plate for detecting the magnetic region, where the magnetic region comprises three concentric tracks. Each track is associated with the sensor over the conductor plate. An axially extending magnetizing device is alternatively arranged on each track along a circumferential direction, so that a south polar region follows a north polar region magnetized along the axial direction.