Step Motors and Drives
by Dennis L Feucht
The step motor is the solution to a problem that no longer exists, that of controlling position when no good power electronics is available. Historically, both motors and electronics developed in the 20th century, but motors were already in use when the first active device, the triode, was invented. Motors preceded the electronics needed to drive them. The brush or dc motor is an ac motor internally (as are almost all motors) with electromechanical phase control implemented out of brushes and commutator bars.
The lack of adequate motor-drive electronics led to the step motor, a motor easy to position with minimal circuitry. Though effective means of controlling and driving all categories of motors that now exist, the step motor is still with us. The history of the development of improved methods of driving it is both interesting and bizarre.
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