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HT-1 is the designation for an experimental high temperature resistant polymeric material under development by the Du Pont Company. It is being developed to fulfill the need for a product which combines durability under high temperature conditions with those mechanical and electrical properties required for acceptable performance in a wide range of industrial end uses. HT-1 can be produced as filament...
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Mica paper was invented at almost the same time in the United States and in France. It was during the war and that is probably the principal reason why its development was delayed.
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The object of this work is to find or develop an epoxy resin system capable of impregnating and embedding magnetic devices wound with various size wires. The resin system should be capable of meeting the environmental requirements of the various military specifications such as MIL-I-16923-C, MIL-E-S400 and MIL-T-27A. In addition, it must have acceptable physical and electrical characteristics. The...
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This study was initiated as part of an overall program to develop some basic information regarding the properties of flexibilized epoxy compounds and to attempt to relate these properties to the composition of the compounds. An additional objective has been to establish the inter-relationships that may exist among these properties. In this study, attention was directed toward the measurement of the...
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Traction motors for diesel electric locomotives are subjected to perhaps the most severe environment imposed on any rotating electrical equipment. Heat, moisture, dirt, chemical contamination and mechanical shock and vibration combine and subject insulation to far greater abuse than found in most industrial applications. And traction motors must give long and reliable service under these demanding...
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The conventional ground insulation system for F.H.P. motors consists of individual slot cell liners and endpunching insulators separating the magnet wire from the magnetic core structure. There has not been a basic change in this ground insulation system for several decades. This suggests that the Insulation Engineer 1. has established the ultimate ground insulation system. 2. is limited by the availability...
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Considerable data are now available relating to the thermal endurance of coated fabrics as a means of temperature classification for the purpose of end use. These data have been largely based on the method of ASTM 1830-61T employing curved electrodes. In order that similar information might be available for users of coated sleeving, an investigation was conducted to develop a method that would subject...
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As a result of recent development efforts by magnet wire manufacturers, new film insulations with improved physical, electrical, chemical, and thermal properties are now available to the electrical industry. Examples of these are modified polyvinyl formal, over-coated polyester, acrylics, epoxies, polyurethanes, and others.
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During the last two decades, in particular, there has been an increasing realization of the importance of the effect of corona discharges on the practical life of electrical insulation under electric stress. During this time there have been numerous papers(1) published particularly in Great Britain and the United States, as well as some significant contributions from other countries, all discussing...
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The development of more accurate and versatile test instruments and the increasing interest in the extension of rotating equipment life through the use of preventive maintenance have resulted in many changes in rotating machines to facilitate maintenance and improve reliability. Most users of electrical equipment are familiar with at least the more fundamental tests and theories and, as a result,...
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Spectacular developments have been witnessed in the latest years in the insulation of large rotating machines such as turbine generators or water-wheel generators in Japan. Among others, application of synthetic resin to stator coil insulation and improvement of corona prevention deserve particular attention.
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The ultimate choice of insulating materials for use in an insulation system for a particular type of electrical equipment is the responsibility of the design engineer. In a partially-developed country like Brazil, however, factors governing this choice may involve so many fields that well-oriented teamwork is sometimes necessary to gather all the information required for a sound decision to be reached...
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Medium frequency electric heating techniques are more and more used by metallurgists to process metals. Schematically, these installations consist of a crucible placed in the middle of a coil in which a medium frequency (MF) current flows.
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One of the major factors governing the selection of magnet wires for rotating machinery designed for higher temperature operation is thermal stability of the insulation.
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A great deal of work has been done, and standards have been developed for the testing of enameled magnet wire in air(1), and for the evaluation of complete insulation systems(2) for induction motors, transformers, and similar electrical equipment. These techniques apparently give excellent correlation with field results when applied to equipment having stationary windings and operating at temperatures...
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An armature varnish is a special type of impregnating varnish. It gives outstanding bond strength to the windings of the wire around the iron core as the armature rotates at speeds of 20,000 to 30,000 revolutions per minute. This paper suggests how this type of varnish can be formulated, tested and applied to armatures that are used for small, high speed motors, such as vacuum cleaners and hand tools...
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Full scale production conversion to a new Class B field coil insulation system for industrial d-c motors and generators was completed at General Electric Company in Erie, Pennsylvania, during the summer of 1960. This system provides a heavy epoxy coil coating applied by a closely monitored and controlled dipping process. The encapsulated coil is then molded to the pole piece to provide a rigidly tight...
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Coatings applied from insulating powders are increasing in importance and reliable methods must be selected for their evaluation. There are no industry standards for measuring these integral films which are formed directly on surfaces and are bonded to them. In addition, there are no generally accepted specifications for the kinds of tests which are most significant. Areas of agreement on measurements...
