10 a spindle 13 is rotatably supported on a bearing housing 12 which is fixedly mounted on a spindle bank 11 of the spinning machine the spindle 13 includes an inner axial portion 23 rotatably supported by means of a foot bearing 29 shown in fig2 on the bearing housing 12 and an outer axial portion 24 coaxial with and fixedly mounted to the inner axial portion 23 and having a bell like sleeve for surrounding the upper axial portion of the bearing housing 12 a rotor 14 is coaxial with and fixedly mounted to the outer axial portion 24 of the spindle 13 and is rotated by a stator 15 in which the rotor is centrally disposed the stator 15 includes a magnetic core 16 of generally square configuration which can be a stack of individual magnetically active plates and a plurality of coils 30 the four corner regions of the magnetic core 16 have a plurality of brackets 17 mounted thereto for securing the individual plates of the magnetic core 16 in stacked relation the brackets 17 retain the individual plates in stacked relation with and are mounted to an interconnecting member 18 which is fixedly mounted by means of a collar to the bearing housing 12 each bracket 17 includes an inwardly facing arcuate shoulder 31 on its lower axial end for cooperating with a compatibly.