An internal permanent magnet synchronous electric machine has a rotor having a body of ferromagnetic material with a plurality of permanent magnets disposed wholly within the body and arranged in the body of the rotor as alternate North and South poles, each North and South pole formed by a pair of the permanent magnets arranged in a V with each magnet being a leg of the V with an apex of the V radially inwardly of ends of legs of the V so that each V opens outwardly in the body of the rotor at an obtuse electrical angle between the legs of the V of 135 degrees ± one degree. The rotor has an outside diameter (Rotor OD) defined in terms of an outside diameter of a stator of the electric machine (Stator OD) as Rotor OD = Stator OD / (1.7 ± 0.5%). Each North and South pole of the rotor has a pole-pitch to pole-arc ratio optimized for minimum cogging torque, maximum torque and optimized core loss.