A stator of a rotary electric machine having secured core slot insulators includes a multi-phase stator winding, having a plurality of slot segments that are adapted to be radially inserted into a plurality of circumferentially spaced axially-extending core slots in a surface of a cylindrically-shaped stator core. The stator winding includes the plurality of slot segments alternately connected at the first and second ends of the stator core by a plurality of end loop segments to form the winding. The plurality of core slots house an insulator to electrically isolate the slot segments from the core slots. The insulator is secured to the sides of the core slot prior to the process of radial inserting the plurality of slot segments into the plurality of core slots of the cylindrically-shaped stator core.