ABSTRACT
The vast majority of DC motors used in servo-controlled systems today are fractional-horsepower, permanent-magnet types. Three dominant factors have influenced this: (1) the development over the past 50 years or so of permanent magnet materials having both high residual flux and high coercive force; (2) the commercial market developed over the last 30 years for computer peripheral devices, requiring motion of one kind or another, largely driven by the revolution in portable computing power and the explosive growth in information storage and graphics reproduction; and (3) the development of power electronics capable of driving these motors and controlling them efficiently. The availability of this “motion control” technology, pioneered roughly between 1970 and 1985, has in turn driven small DC motors into many other markets, including consumer electronics and automotive accessories. Table 3.1 is an attempt to summarize these trends as they exist today.
