A permanent magnet assembly comprising: an arc-shaped flux return section formed of magnetically permeable material and extending along a portion of an arc and having an upper portion with a first end and a second end, a lower portion with a first end and a second end, and a middle portion with a first end and a second end, wherein the first end of the upper portion is operatively coupled to the first end of the middle portion and the first end of the lower portion is operatively coupled to the second end of the middle portion, wherein the middle portion of the arc-shaped flux return section is positioned on the exterior of the permanent magnet assembly such that an opening of the arc-shaped flux return section faces toward a central axis of rotation of the permanent magnet assembly and wherein the permanent magnet assembly is adapted to rotate about the central axis of rotation; an upper arc-shaped permanent magnet section having a north end and a south end, wherein the north end of the upper arc-shaped permanent magnet section is operatively coupled to the second end of the upper portion of the arc-shaped flux return section; and a lower arc-shaped permanent magnet section having a north end and a south end, wherein the south end of the lower arc-shaped permanent magnet section is operatively coupled to the second end of the lower portion of the arc-shaped flux return section; wherein an arc-shaped gap is formed between the south end of the upper arc-shaped permanent magnet section and the north end of the lower arc-shaped permanent magnet section, wherein the arc-shaped flux return section, the upper arc-shaped permanent magnet section, the lower arc-shaped permanent magnet section, and the arc-shaped gap are arc-shaped with reference to the central axis of rotation of the permanent magnet assembly and wherein the magnetic field in the arc-shaped gap is in a direction parallel to the central axis of rotation. an arc-shaped flux return section formed of magnetically permeable material and extending along a portion of an arc and having an upper portion with a first end and a second end, a lower portion with a first end and a second end, and a middle portion with a first end and a second end, wherein the first end of the upper portion is operatively coupled to the first end of the middle portion and the first end of the lower portion is operatively coupled to the second end of the middle portion, wherein the middle portion of the arc-shaped flux return section is positioned on the exterior of the permanent magnet assembly such that an opening of the arc-shaped flux return section faces toward a central axis of rotation of the permanent magnet assembly and wherein the permanent magnet assembly is adapted to rotate about the central axis of rotation; an upper arc-shaped permanent magnet section having a north end and a south end, wherein the north end of the upper arc-shaped permanent magnet section is operatively coupled to the second end of the upper portion of the arc-shaped flux return section; and a lower arc-shaped permanent magnet section having a north end and a south end, wherein the south end of the lower arc-shaped permanent magnet section is operatively coupled to the second end of the lower portion of the arc-shaped flux return section; wherein an arc-shaped gap is formed between the south end of the upper arc-shaped permanent magnet section and the north end of the lower arc-shaped permanent magnet section, wherein the arc-shaped flux return section, the upper arc-shaped permanent magnet section, the lower arc-shaped permanent magnet section, and the arc-shaped gap are arc-shaped with reference to the central axis of rotation of the permanent magnet assembly and wherein the magnetic field in the arc-shaped gap is in a direction parallel to the central axis of rotation.