Electric rotating machine and electric power steering apparatus

An electric rotating machine which comprises:

• a stator;
• and a rotor located on a radially inner side of the stator,
• wherein the stator is provided with:
• an iron core having an annular portion and multiple tooth portions extending from the annular portion to its radially inner side and circumferentially arranged to be spaced apart from each other;
• and windings wound around the tooth portions;
• wherein the rotor is provided with multiple rotor blocks each having:
• a central body whose outer shape in cross-section perpendicular to its shaft center is a regular polygonal shape;
• and multiple permanent magnets placed on respective multiple flat portions of the central body corresponding to respective sides of the regular polygonal shape, said permanent magnets each having a cross-section perpendicular to the shaft center whose radially outer side is arc-like and whose radially inner side is linear;
• wherein the multiple rotor blocks are aligned in an axial direction while being shifted in a circumferential direction from each other by a preset angle, and are rotatable integrally;
• wherein the tooth portions are each provided with, at its head, flange parts circumferentially projecting toward heads of its adjacent tooth portions;
• wherein the permanent magnets each have, at its circumferential center, a maximum height from the flat portion;
• wherein the number of the tooth portions is 3N;
• wherein the shape of the central body is a 2N-sided polygonal shape;
• wherein the permanent magnets each have a minimum height near an end of the flat portion;
• wherein the rotor has two rotor blocks as said multiple rotor blocks;
• wherein said “N” denotes a natural number;
• and
• wherein, in order to reduce a torque ripple during rotation to 1% or less,
• a product of the angle and said “N”, is set to be more than 25.2 and less than 40.0,
• a ratio of the minimum height of the permanent magnet to the maximum height of the permanent magnet is set to be more than 0.355 and less than 0.455;
• and
• a ratio of a flange-part root radial thickness at a root of the flange part to the maximum height of the permanent magnet is set to be less than 0.66.