Switched reluctance motor with indirect position sensing and magnetic brake

DETAILED DESCRIPTION In general terms, a switched reluctance motor designed in accordance with this invention includes a rotor that rotates about an axis and has a plurality of rotor poles.
A stator that is stationary about the rotor axis generally surrounds the rotor.
The stator also includes a plurality of poles and the rotor poles move into and out of alignment with the stator poles when the rotor rotates about its axis.
A main current conducting coil that has a first inductance is disposed about at least one of the stator poles.
An auxiliary current conductive coil is disposed about the same stator pole such that an inductance ratio of the main coil to the auxiliary coil is constant irrespective of a position of the rotor poles relative to the stator poles.
The auxiliary coil has a second inductance that is greater than the inductance of the main coil.
A selectively controllable current source individually energizes the main coil and the auxiliary coil, respectively, to thereby produce a magnetic flux that controls whether the rotor rotates about its axis, relative to the stator.
A voltage sensor determines a voltage across the auxiliary coil when the auxiliary coil is energized by the current source.
Means for determining a difference in a current phase value, which is associated with a current in the auxiliary coil, and a voltage phase value, which is associated with the voltage across the auxiliary coil, provides a signal that is indicative of the position of the rotor poles relative to the stator poles.
The methodology associated with this invention for controlling a switched reluctance motor includes four basic steps.
First, a main coil, which is disposed about a stator pole, is energized such that a motion inducing current is established in the main coil.
The current in the main coil causes a rotor to rotate relative to the stator pole.
Second, it is determined whether the rotor has reached a preselected rotation condition.
Next, an auxiliary coil, which is disposed about the same stator pole such that a constant inductance ratio of the main coil to the auxiliary coil is established, is energized such that a current is established in the auxiliary coil