The authors report the characteristics of dual-coat magnet wires with heat-resistant, self-lubricating (SL) overcoat and the results of their application to the actual production of electric motors. The newly developed heat-resistant lubricating varnish enables production of magnet wires with improved lubricating properties and thermal and mechanical strength in combination with an insulating film such as polyester, modified polyester, polyamideimide, etc. as undercoat material. It was found that improvement of lubricating property was an effective measure to ease mechanical stress during manufacturing. A possibility of reducing film thickness due to the improvement was suggested. and confirmed by a breakdown test using coils wound into actual motors. The class F and class H SL magnet wires have successfully been used for stator coils of general-purpose medium size motors and for servomotors, respectively. They helped make these motors better, lighter, and more efficient. with expanded use of automated manufacturing.
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