J Electr Eng Technol.2015; 10(4): 1700-1711 http://dx.doi.org/10.5370/JEET.2015.10.4.1700 1700 Copyright ⓒ The Korean Institute of Electrical Engineers This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/ licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Electrical and Thermal Characterization of Organic Varnish Filled with ZrO 2 Nano Filler Used in Electrical Machines D. Edison Selvaraj † , R. Vijayaraj* and C. Pugazhendhi Sugumaran** Abstract – In the last decade it has been witnessed significant developments in the area of nano particles and nano scale fillers on electrical, thermal, and mechanical properties of polymeric materials such as resins, varnishes, enamel and bakelites. The electric and thermal properties were more important in the electrical equipments for both steady state and transient state conditions. This paper deals with the characterization of the electric and thermal properties of the pure varnish and zirconia (ZrO 2 ) filler mixed varnish. The electric properties such as dielectric loss (tan δ), dielectric constant (ε), dielectric strength and partial discharge voltage were analyzed and detailed for different samples. It was observed that zirconia nano filler mixed varnish has the superior dielectric and thermal properties when compared to those of standard varnish. It has shown that at power frequency the 1wt% nano composite sample has the higher permittivity value when compared to other samples. It has been examined that the 1wt% sample was having higher inception and extinction voltages when compared to other samples. It has been observed that 1wt% sample has higher dielectric strength when compared with other samples. There has been an improvement of thermal property by adding few weight percent of zirconia nano fillers. There was not much variation in glass transition among the nano mixed composites. The weight loss was improved at 1wt% of the zirconia nano fillers. Keywords: Zirconia, Nano fillers, Varnish, Dielectric strength, TGA 1. Introduction In Different types of insulating medium such as gas, solid, vacuum, liquid and composite was used for electrical power apparatuses. The important parameters considered for selecting the dielectric materials were Dielectric strength, Conductivity, Dielectric constant, Loss factor, Flash point, Gas content, Viscosity, Mechanical strength, Compressive strength, Bonding strength, Surface resistance, Tracking resistance and Chemical properties. Organic varnishes and solvent less resin were widely used in the Insulation system of electrical machines for impregnation and finishing applications [1-3]. Impregnating and finishing agents offer several advantages, such as increased mechanical bonding to the winding wire, improved dielectric properties, improved thermal conductivity and protection to the winding against moisture and chemically corrosive environment. Elmo Luft 1A-FD was an anti tracking finishing varnishes having phenolic chemical base. It was an insulation of class B having the temperature limit of 130°C. It has the following distinctive characters such as fast air drying, anti-tracking and clear. It was used for Coating on PCB, SRBP components, impregnation of small coils and stators. The basic characteristic of dielectric materials were expressed in terms of mechanical, thermal, electrical, magnetic optical, chemical and physical properties. The behaviour of the dielectric materials under applied forces and loads were determined by means of mechanical properties. Some of the important mechanical properties were stiffness, ductility, hardness, toughness, creep and malleability. Thermal properties were used to determine the behaviour of the dielectric materials when they were subjected to variation in temperature. The most important thermal properties needed for the dielectric materials were specific heat, thermal expansion, thermal conductivity and thermal shock resistance [2]. These properties were needed to determine the thermal withstanding capacity and the life time of the apparatuses when they are subjected to the thermal changes. Heat was developed in the motor due to the loads and over voltages. Thermal withstanding capacity depends upon the amount of the heat produced by the windings of the motor under the loaded condition. The heat produced under the different conditions of the load can be found by heat run test whereas the heat produced by over voltages cannot be found. The heat produced by the motor at the different load conditions would be helpful for determining the life time of the motor. Heat produced by the over voltages would damage the windings of the motor and the amount of heat produced due to over voltages cannot be found by normal heat run test. The dielectric property depends upon the atomic structure of the material. For crystals, the dielectric † Corresponding Author: Dept. of Electrical and Electronic Engineering, Panimalar Engineering College, Chennai, India. (edisonsivakasi@ gmail.com) * Dept. of Mech Engineering, Dhanalakshmi Srinivasan College of Engineering and Tech, Mamallapuram, Chennai, India. (vijayme2k @yahoo.co.in) ** Division of High Voltage Engineering, College of Engineering, Guindy, Anna University, Chennai, India .(cpsugumar@gmail.com) Received: October 24, 2014; Accepted: November 10, 2014 ISSN(Print) 1975-0102 ISSN(Online)2093-7423