Thermal aging properties of mica/epoxy stator winding insulations

Electrical properties such as ac current and tans of mica/epoxy composite materials(130 mu m) were measured Schering bridge. Their surface conditions were characterized using scanning electron microscope(SEM), Fourier transform infrared(FTIR), differential scanning calorimeter(DSC) and thermogravimetric analysis(TGA) in sound and aged specimens. Both ac current and tan delta of sound specimens were higher than those of aged specimens. FTIR results show a new peck at 1710 cm for aged specimens, originating from carbonyl group formed bg the oxidation reaction during process. Glass transition temperatures of aged specimens are observed to be 95.43 degrees C and 113.43 degrees C, which increases with the increase of aging time. TGA results indicate that the sound specimens contain a smaller amount of volatile components than the aged specimens.