Electrical insulating properties of some varnish compositions Available to Purchase

The dielectric constant (E′), dielectric loss (E″) and power factor (tan §) were measured for various excess hydroxyl content resins (polyesteramide, alkyd/polyesteramide and alkyd resins) and also for their corresponding dry films. Measurements were conducted within the frequency band 105 to 107 Hz and temperature range 20–50°C. The various parameters affecting the dielectric behaviour of resin varnishes and their dry films are discussed. Also the effect of ageing at 110°C upon the dielectric behaviour of dry films is another parameter taken into consideration.