Cogging torque due to roundness errors of the inner stator core surface

Cogging torque of brushless permanent magnet (PM) motors employing segmented stator cores with narrow slot openings has been investigated. Two types of test motors were examined: one with a segmented Halbach cylinder rotor and the other with a radially oriented ring PM rotor. The measured cogging torque was predicted from the measured dimensional errors for the inner radius of the stator core in both types.