In the emergence of switched reluctance motors to the commercial market, two-phase motors have received relatively little attention. Higher power and industrial applications have focused on the use of three and occasionally four phase machines, while low cost applications demanding only modest performance have largely been the domain of single phase machines. By contrast, while two phase systems have been the subject of occasional studies, they have not been widely applied.

Two phase systems represent a compromise between the higher cost but higher performance three phase machines, and the lower cost but lower performance single phase systems. They do not suffer from the same magnitude of peak to peak torque ripple that single phase machines experience due to their wide zero torque arcs. Yet two phase systems keep a relatively low component count in their power-converter designs. The primary drawback to two phase motors is the difficulty of torque production at startup speeds. Although sizably reduced from single phase machines, the zero torque regions in two phase machines can still result in rotor lock unless steps are taken to circumvent them. These steps can include measures such as: placement of permanent magnets or other means to ensure the rotor is positioned outside of these zero torque regions when at rest, mechanically spinning the motor before energizing the phase windings on startup, shaping of the rotor or stator poles to extend the positive torque regions of each phase, or use of the machines mutual inductance with both phases energized to produce enough torque to initiate motion.

This project is intended to develop a variable speed controller for a 4:6 two-phase switched reluctance motor. The motor is to operate in all four quadrants, and is to demonstrate self starting capability. The controller is also supposed to produce signals needed to operate the motor with multiple converter designs. Two different converter designs will be built and tested with the converter. One makes use of a single switch and two diodes per phase, the other has one switch and one diode per phase plus a common switch and common diode shared by all phases.

There are many possible applications of the system being developed in this project. Any application needing four quadrant operation while still being constrained by low cost requirements would be ideal. Some examples include washing machines, power tools, and low power industrial applications.