Effect of rotor profiles on the torque of a switched reluctance motor

The effects that simple variations of the standard rotor pole face profile could have on the torque are examined, basically from an elementary viewpoint of how the modified profiles affect the distribution and magnitude of the radial and tangential components of the flux density. It is observed that the average torque is mostly affected by changes that alter the dominant radial component, such as changes in the effective airgap length. It was also observed that an increase in the average torque can be obtained by a favorable shift in the torque versus angle characteristics by relatively simple changes of the rotor pole profile. Such a shift that reduces the slope of the torque angle characteristic, skewing the curve towards the unaligned position, has two advantages. One is that the phase inductance is at its maximum positive slope, and hence maximum torque, when the phase is energized. The other is that the flatter inductance profile near the aligned position when the phase current is to be commutated allows a faster drop-off of the commutated current, and thus a smaller negative torque.<>