Since the 1980s, permanent magnet AC servo drive technology has outstanding development with integrated circuits, power electronics and variable speed AC drive technology. Many well-known electrical manufacturers all over the world have launched their own AC servo motor and servo drive series products and constantly improve and update them. AC servo system has become the mainstream of modern high-performance servo system gradually eliminating the DC servo system. Since 1990s, the world has commercialized the sine-wave AC servo drive fully digital controlled is applied to the ac servo motor system already commercialized around the world. AC servo drive is in a rapid development.
AC servo motor is constructed of two parts, namely the stator and the rotor . The stator has the same structure as the resolver. And in the stator core also lies two-phase windings with a angle of 90 degrees to each other. One of the winding is magnet field winding, and the other controlling winding. If the variable voltage Uf is exerted on both ends of the excitation winding, AC servo motors will start to rotate soon. Current from the field winding and control winding generate a rotating magnetic field within the motor and the direction of the motor depends on that of the magnetic field.