A brushless motor-generator includes a rotor having a ferromagnetic tube with radially polarized, alternating polarity permanent magnet poles, and an air core armature that magnetically exerts torque upon the rotor. The magnetic poles drive magnetic flux across a radial magnetic air gap inside of the tube and through windings of the armature that are located in the air gap. The windings utilize wire that is comprised of multiple individually insulated strands that are bundled together and sheathed in an outer electrically insulating serve that separates adjacent windings and provides a higher dielectric breakdown strength than the insulation on the individually insulated strands. A thin circumferentially tensioned band is wrapped around the outer diameter of the axially traversing portions of the windings where located inside the magnetic air gap, imparting radial compression and structural integrity to the windings and increasing the circumferential structural strength of the air core armature for torque production.