Abstract: A blood pump having a pump casing with a blood flow inlet and a blood flow outlet, an impeller arranged in said pump casing so as to be rotatable about an axis of rotation. The impeller has blades sized and shaped for conveying blood from the blood flow inlet to the blood flow outlet. There is a drive unit for rotating the impeller, the drive unit having a magnetic core including a plurality of posts arranged about the axis of rotation and a back plate connecting the posts and extending between the posts in an intermediate area. A coil winding is disposed around each of the posts. The coil windings are controllable so as to create a rotating magnetic field. The impeller has a magnetic structure arranged to interact with the rotating magnetic field so as to cause rotation of the impeller.