| abstract |
Electric field easing members (corona rings) for easing concentration of electric fields caused at edges of a core are disposed between the core and a winding to form a gap so to allow the presence of a cooling medium (insulating oil) between the top and bottom surfaces of the core and the electric field easing members. Thus, pressboards between the core and the electric field easing members become unnecessary, a wire-wound apparatus can be prevented from having a short service life due to the degradation of the pressboards, and the pressboards can be made to have a long service life because the electric field easing members are not heated by thermal conduction from the core. |