Izvorni znanstveni članak
https://doi.org/10.1080/00051144.2020.1761100
Critical stress of oval foil winding with epoxy coated insulation determined using measured equivalent modulus of elasticity
Nina Meško
; Končar Distribution and Special Transformers Inc, Zagreb, Croatia
Branimir Ćućić
; Končar Distribution and Special Transformers Inc, Zagreb, Croatia
Damir Žarko
; Faculty of Electrical Engineering and Computing, University of Zagreb, Zagreb, Croatia
Sažetak
In the distribution transformers design oval windings are used due to economic advantages. On the other hand, such windings are more susceptible to radial forces in a short circuit. A diamond dotted paper with an epoxy coating is used in order to increase the stiffness of the winding. Despite that, winding failure may occur during the short circuit, e.g. buckling of inner winding. Because of a very thin foil conductor (typically 0.5–2 mm), the most critical is inner low voltage foil winding which can collapse due to radial forces at stresses far below the elastic limit of conductor material. This paper shows an analytical approach to the calculation of critical stress in inner oval foil winding with epoxy coated insulation. Critical stress was calculated using the equation for free buckling of round winding. Equivalent Young's modulus of elasticity was obtained experimentally from the testing of the sample model loaded with bending force on a tensile test machine. A total of 12 test samples were formed from aluminium foil conductor and diamond dotted paper and cured at the temperature of 105°C. The results were successfully verified on distribution transformers subjected to short circuit withstand tests.
Ključne riječi
Distribution transformer; short circuit; critical stress; oval foil winding; diamond paper; Young’s modulus of elasticity
Hrčak ID:
239880
URI
Datum izdavanja:
25.6.2020.
Posjeta: 960 *