A look at several Two-Phase Hybrid Step Motors and their dominant error sources, and comment on how the errors are overcome by true servo operation of these motors.

Transverse magnetic flux motors -- also known as step motors -- become Hybrid Servos when you operate them closed loop. This is the same transformation that happens between running a 3-phase synchronous motor from line voltage as opposed to running it closed loop as a brushless servo. In the case of hybrid motors, there are many degrees of what is advertised as "closed loop," and thus significant differences in the performance improvements seen.

The transverse flux permanent magnet motor -- also known as a hybrid step motor or hybrid servo motor -- has a wide range of performances, depending upon how you drive these motors, and whether you operate them in open loop or one of the many variants of closed loop methods you use. In this third installment we will cover some of the many ways to drive these motors, as well as how these choices affect the performance of these motors.