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A broad comparative study of the causes of electric motor failure is difficult to accomplish. Motor manufacturers are involved in failure studies, as such, but only as far as is appropriate to satisfy warranty requirements. Once the warranty period has passed the motor manufacturer almost never is advised of the cause of failure and, as a result, an attempt by the manufacturer to continue a failure...
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High voltage ac motors with ratings from a few hundred kW may, during normal operation, be subjected to steep-fronted impulse voltages which can be hazardous to the turn-to-turn insulation. The rise time of these impulse voltages can be as short as 0.2 microsecond. These problems were discussed by R. M. Sexton in a recent paper1 where further references can be found.
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The need to know the effects of temperature on electrical insulation was first analyzed and discussed when Steinmetz and Lamme published their paper in 1913 entitled “Temperature and Electrical Insulation”.1 This classic paper not only reflects the generally accepted concepts of their day but also introduces the theory that insulation deteriorates over a period of time at certain given temperatures.
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The purpose of this paper is to report on the reaction of typical commercial grades of laminated plastics to tests of their mechanical and electrical endurance under aircraft environments.
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Typically a gas is almost a perfect electrical insulator which allows its widespread use in that capacity. When an electric field of sufficient intensity is applied across a gas, it can become an electrical conductor. The transition from the electrically insulating state to the electrically conducting state is called electric breakdown. This paper is a tutorial attempt to review the fundamental physical...
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This paper will describe two methods of significantly improving the reliable insulating ability of concentric-gap gas-filled systems. The first of these makes use of a thin dielectric coating bonded on one or both concentric conductors. The second utilizes the field of the concentric line to remove free conducting particles electrostatically from the system.
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In recent years more and more attention has been directed to the development of electrical equipment operating at cryogenic temperatures. The application of superconductors in high field magnets is well known, but superconductivity appears to be less advantageous for devices such as cable and transformers. Instead, the low resistance of copper and particularly of very pure aluminum at liquid hydrogen...
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Perhaps the most familiar property of a dielectric material is the capacitance increase observed when a sheet of dielectric is inserted between the plates of an “air” capacitor. In fact, the ratio of dielectric to air-filled capacitance is often used to define the dielectric constant ε'. Defined in this way, its magnitude becomes a property of the material, independent of the measuring voltage or...
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Epoxy impregnants are being used in many applications for the environmental protection of magnet coils in motors, transformers, solenoids and reactors, and even for completed electronic circuit functional blocks. The physical properties of the epoxy resin compounds used are ideally suited, in most cases, for this purpose. These properties may be varied from rigid to flexible, transparent to opaque,...
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The subject of this session relates to Electrical Insulation Systems and it is to such systems or more particularly to one such system that I wish to direct attention.
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The breakdown of end turn insulation in high voltage rotating equipment due to “tracking” appears to be an often unrecognized cause of failure. End turns insulation of form wound coils often becomes coated with dirt when machines operate in contaminating environments. In the presence of high humidity, the contaminant coating be comes conductive. If a leak in the insulation permits current to flow...
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Premature failure of rotating equipment may be caused by improper selection of varnish and wire. Proper selection has become more difficult because of the multitude of new wire and varnish polymer systems which have recently evolved. Some of these systems do not exhibit straight line thermal degradation curves. Further, too much emphasis has been given to system selection based upon thermal life data...
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As a result of the incorporation of very high impedance devices and components such as operational amplifiers and field effect transistors on etched circuits, the insulation resistance of the reinforced laminate substrate begins to approach those of electronic components. All of the factors which reduce this insulation resistance, such as increasing temperature, high humidity and contamination, become...
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During supersonic flight of the F-111 aircraft, high temperatures are developed in the airstream around some portions of the pullout cable assemblies which electrically join externally mounted armament to the aircraft. Therefore, construction materials and associated components in these assemblies must be capable of surviving certain temperature extremes and must reliably perform a subsequent set...
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By the way of introduction to you who are not familiar with Sandia Laboratory and its operations, I will give you a few pertinent facts about Sandia. We are located in the eastern edge of Albuquerque, New Mexico, and work with the Los Alamos Scientific Laboratory in the design and development of hardware for nuclear bombs and missiles. In general this hardware may be described as ballistic cases,...
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The moisture conditioning cycle is recognized as probably the most critical factor in the functional evaluation of rotating machinery insulation systems. An analysis is made of some of the humidity problems currently existing, particularly in respect to the use of the now proposed IEEE 117 Test Procedure and the NRL designed condensation chamber. A time dependence ratio of surface to bulk absorption...
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Providing the most dependable electric service to the maximum number of users at the lowest possible cost has been, and continues to be, the primary goal of the electric utilities of this country. There was a time, in the earlier years of the industry, when the realization of each of these goals presented a real challenge. However, over the years, technological progress has been steady, the goals...
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Insulation resistivity was measured as a function of temperature and electrical stress on slabs of solid dielectric. These data were empirically fitted to a resistivity equation using a time-sharing computer. The transcendental stress equation is then solved for each dielectric using a computer program written for this purpose. Parameters which affect stress distribution are temperature, electrical...
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Over the past 40 or more years, the electric utility industry has met and solved a variety of problems and challenges. Let me pose some possible future problems, mainly to try to explain to the skeptical why a utility man might be interested in microwave power transmission. Admittedly, the probability that these particular problems will actually arise is not very great, but that is beside the point;...
