Design of permanent-magnet alternators

PERMANENT-MAGNET alternators have been used for many years in small-sized units such as tachometer generators, governor frequency sources, and magnetos, but until recently have not been adopted widely as primary sources of power. With the development of dispersion-hardening alloys typified by the Alnico family and their application to rotating machinery, the permanent-magnet alternator has assumed a more important role for power applications. In some ratings these machines weigh less, consume less space, and cost less than d-c excited alternators. The saving in weight and space is accomplished chiefly by the elimination of the d-c exciter. When the exciter is absent, commutation problems are eliminated. Hence, these machines are assuming an important role for portable, aircraft, and other applications in which the saving of weight is an essential factor.