a heat exchange system for an electromagnetically operated print hammer of a print hammer bank provides internal and external heat transfer for the operating windings . a non - magnetic metal bobbin of the heat exchange system provides conductive transfer of heat from the interior of the operating winding to the magnetic core . flat parallel plates of magnetic material are attached to the sides of the operating winding for external heat transfer and magnetic flux shielding . the plates may have multiple laminations having different saturation and permeability characteristics .