Variable reluctance motor structures for low speed operation

A linear analysis is used to compare the static torque produced by a mutually coupled variable reluctance motor to that produced by a conventional SRM (switched reluctance motor). A similar analysis has also been completed to compare the static torque of a variable reluctance motor with anisotropic rotor to that produced by an SRM. The motors were compared on the basis of fixed source voltage and current. It is shown that for motors with a similar number of poles and phases, the maximum improvement in static torque of the mutually coupled motor over that of the SRM is 200% while the maximum improvement in static torque of the anisotropic motor is 222% over that of the SRM. However, end turn length differences and saturation tend to reduce the benefits from these designs. Effects associated with end turn length due to aspect ratio pole, and phase combinations have also been studied. It is shown that the greatest benefit from the alternative variable reluctance structures occurs for low diameter to length ratio and a small number of poles and phases