Permanent-magnet fields for synchronous machines — I

PERMANENT-MAGNET generators have been built with ratings ranging from a few watts up to many kilowatts. Figure 1 shows a 0.1-kw rotor suspended from a 75-kva unit and even larger capacities and higher speeds are possible. The armature of permanent magnet alternators may be of conventional design, but the field structure is inherently different and in the last 6 years a rotor structure has been developed which is sound mechanically, efficient magnetically, and simple to manufacture.