Capacitively commutated brushless DC servomotors

There are disclosed both one- and two-dimensional, high resolution, brushless DC servomotors that are linear, rotary, planar and cylindrical in nature. All of these employ a capacitive method for deriving the required position and motor commutation information. In suitable circumstances, particularly two-dimensional planar motors on air bearings, the method allows the use of the motor ferromagnetic cores themselves as the capacitive position sensing elements. This leads to a particularly simple and compact type of servomotor design. In addition, since such motors can move at high spead, there are also disclosed two transformer coupled methods for handling the current drive to the motor windings. Both methods are simple, energy efficient, applicable to motors of any number of phases, and in addition, handle motor direction reversals automatically.