Enameled Wire Research Articles

Effect of long‐term oxidation at 200–300°C on six types of aromatic amide and imide resins

AbstractSix types of aromatic amide and imide resins in the form of wire enamels, paper, and film were subjected to thermal and oxidative deterioration at temperatures ranging from 200 to 300°C and for aging periods of 3 and 6 months. No HCN was evolved at any temperature and aging time. The main degradation product was, in all cases, carbon dioxide, in quantities increasing as functions of time and temperature. Other materials evolved were, in approximate order of magnitude, carbon monoxide, water, and nitrogen. Traces of acetonitrile were recovered from a film and a paper sample, while benzene, also in trace quantities, was evolved from the wire enamel samples at temperatures ranging from 250 to 300°C.

Apparatus and Procedures for Evaluating Dielectric Properties of Wire Enamels in Controlled Environments

Methods are described for measuring intrinsic dielectric properties of wire enamels and wire enamel-varnish combinations in controlled environments. Random wound bifilar coils serve as test specimens and environment control is achieved by suspending these coils in a pressure tube connected to a gas handling system. Dielectric properties have been measured at pressures ranging from vacuum to 32 atmospheres and at temperatures from -40° to 350°C. Typical results are reported which illustrate utility of the apparatus and procedures. The importance of measuring dielectric properties at elevated temperatures is stressed and a method for establishing a practical thermal limit tmax is described. It is demonstrated that in a controlled environment, tmax, is a characteristic intrinsic property of an insulating material. Interpretation of typical conductance-temperature data according to the theory of rate processes, suggests that tmax corresponds to a temperature at which the polymer undergoes significant changes in viscoelastic behavior. There is evidence that the mechanism of ac conductance below tmax is by polarization, while above tmax conductance results from ion movement. The influence on tmax of degree of cure, frequency of the applied voltage, and nature of the atmosphere surrounding the insulating material, is discussed.

Fume Control in Wire Enameling by Direct-Flame Incineration

The results of source tests to demonstrate the applicability of direct-flame incineration for the control of the effluent from a wire-enameling bake oven are presented. The tests were conducted with a portable direct-flame incinerator under actual plant conditions. The efficiency of direct-flame incineration was established at incineration temperatures of 1000F, 1200, and 1400°F. Evaluation of incineration efficiency was performed by both analysis and quantitative odor measurement using an odor panel.

Thermal Endurance of Polyester Enameled Wires Using Twisted Wire Specimens: Statistical Analysis of Final Test Results

Thermal endurance tests to AIEE Standard 57 [1] have been performed in six laboratories each using self-prepared varnished specimens made from a common sample of polyester enameled wire and polyester varnish. The results have been analyzed to test the hypothesis of the departure from linearity of the relationship between the logarithm of life and the inverse of the absolute temperature. A comparison is made between the experimental results at the lowest test temperature and the corresponding extrapolated values based on the experimental results at the higher temperatures. The variation between the results of different laboratories is considered. Comparison is made with previous work [2] undertaken in six laboratories on PVA enameled wire specimens, prepared and impregnated with an oil-modified phenolic varnish by a single laboratory, and with published AIEE results. Comparison is also made with the results of a previous interim statistical analysis, [3] applied to the test results at the three higher temperatures only. The main statistical analysis is performed both for the complete set of results, and for the median results only. The extrapolated thermal lives based on the two methods are shown, with one exception, to differ by less than 6 percent at 20°C below the lowest test temperature. The importance of the median method is that generally not all of the specimens are required to be tested to failure, with a consequent saving of a substantial amount of testing time, particularly at the lowest test temperature.

Interaction of Varnish with Magnet Wire Enamel

The interaction of varnish with magnet wire enamel can lead to a reduction in the thermal life rating of the insulation system (ASTM D2307-64T). The recognition of this reduction in life rating is encountered first by varnished twisted pairs of enameled wire. An attempt is made to determine the mechanism of this interaction by studying the system microscopically, by differential thermal analysis and by infrared analysis. The microscopic analysis defines the nature of the bond between magnet wires and the type of coverage that the varnish gives to the magnet wire. It also reveals some information on the type of attack on the enamel and varnish system. Thermal analysis and infrared analysis are used to determine, if possible, whether the thermal decomposition of the magnet wire enamel is accelerated by the presence of the varnish and to reveal some background information as to the nature of this accelerated decomposition. This can then act as guide for the selection of varnishes with enamels that will minimize interactions that reduce the thermal life of insulation.

We have used new technology to develop AMOCO AI Wire Enamel. You can coat wire better at lower cost. Is that square?

We have used new technology to develop AMOCO AI Wire Enamel. You can coat wire better at lower cost. Is that square?

We have used new technology to develop AMOCO AI Wire EnameL You can coat wire better at lower cost. Is that square?

We have used new technology to develop AMOCO AI Wire EnameL You can coat wire better at lower cost. Is that square?

AI polymer laminates for high temperature stability

AbstractAmoco AI amide imide polymer is an all aromatic polymer which is currently being used as a high temperature wire enamel. It also looks promising as a high temperature laminating material. It is available in a stable solid form and is readily formulated in its laminating solvents. B‐Staged coated glass cloth with excellent shelf stability is easily prepared. AI laminates retain their initial flexural strength after four weeks at 500°F. They retain 50% of their initial flexural strength after one week at 572°F. Other modifications of this type of polymer are being investigated as laminating materials.

Thermal Endurance of Polyester Enameled Wires Using Twisted Wire Specimens. Statistical Analysis of Test Results

Thermal endurance tests to AIEE Standard 57 [1] have been performed in six laboratories each using self-prepared varnished specimens made from a common sample of polyester enameled wire and polyester varnish. The results have been analyzed to test the hypothesis of the departure from linearity of the relationship between the logarithm of life and the inverse of the absolute temperature. A comparison is made between the experimental results at the lowest test temperature and the corresponding extrapolated values based on the experimental results at the higher temperatures. The variation between the results of different laboratories is considered. Comparison is made with previous work [2] undertaken in six laboratories on PVA enameled wire specimens, prepared and impregnated with an oil-modified phenolic varnish by a single laboratory, and with published AIEE results. Comparison is also made with the results of a previous interim statistical analysis, [3] applied to the test results at the three higher temperatures only. The main statistical analysis is performed both for the complete set of results, and for the median results only. The extrapolated thermal lives based on the two methods are shown, with one exception, to differ by less than 6 percent at 20°C below the lowest test temperature. The importance of the median method is that generally not all of the specimens are required to be tested to failure, with a consequent saving of a substantial amount of testing time, particularly at the lowest test temperature.

Some Relations of Thermal Cycling to Thermal Life Temperature Classification of Enameled Wire Determined by AIEE 57 Test Procedures

The industry has long recognized that thermal cycling and thermal shock resistances of enameled wire play an important part in determing the thermal life by AIEE 57 test methods. Data are presented for varying thermal cycling indicating significant arivariation of temperature classification roughly from Class 155°C to Class 105°C for the same wire enamel. It is also shown that if the thermal cycling procedure is held constant, reasonable conformity of test results can be expected.

The behavior of polypyromellitimide resins at high temperatures

Aromatic polyamides and polyimides of high molecular weight are currently under development by many industrial laboratories. Wire enamels, laminating and impregnating resins, and varnishes incorporating this new class of thermally stable polymers withstand higher operational temperatures than do most organic polymeric materials in use today. The thermal and oxidative stability of two of these resins has been investigated in air, in oxygen, and in O18-enriched oxygen over a temperature range of 300–400°C. The mechanism of degradation is postulated to be that of a unit by unit destruction of the polymer.

Automatic inspection—cybernetic machines

The economic reasons for introducing automatic inspection equipment in process and automatic assembly lines are reviewed and it is concluded that cybernetic or self-steering machines are essential for the multi-point inspection system. Two early examples of automatic inspection equipment are described—a device for locating pin-holes in enamelled copper wire, and a tungsten filament crystal-cleavage tester. The problem of dealing with tolerances on interdependent dimensions is discussed and inspection output logic units are proposed which can carry out automatic limit shifting. An analogue storage device is sometimes useful when a series of successive measurements are made. Stability and machine speed are considered. The cost of automatic inspection equipment is reviewed and the technical and financial considerations involved in adopting the techniques are discussed in general terms.

Aging studies on transformer insulating materials (Class A) by means of infra-red spectroscopy

Aging tests have been carried out both on wire enamel and varnished wire enamel samples. The samples were tested for dielectric strength at 60 c/s at different stages of aging. After the insulation had been removed from the wire, it was analysed in an infra-red spectrometer. The spectra showed gradual changes with increased amount of aging, particularly in the CH stretching and OH stretching absorption bands. These data were correlated with other measured parameters of the material, particularly breakdown voltage, and the possibility of the existence of such a correlation has been found. The data from the spectra can also be used to determine an approximate value of the rate constant B of the Arrhenius equation.

ポリエステルエナメル線の性質に及ぼす焼付け温度とポリエステルの官能基度の影響

テレフタル酸ジメチル, エチレングリコールおよびグリセリンからエチレングリコールとグリセリンの配合割合を変えて官能基度の異なるポリエステルを合成した。グリセリンの混合割合の多いものは重縮合反応速度が遅く, 生成ポリエステルの反応率が低い。ポリエステルの流出量～温度曲線から官能基度の小さいものは融解温度が高く結晶性であること, および熱分解曲線から縮合反応と熱分解反応の起こる温度範囲が接近していて, 実際の焼付け温度ではこの両反応が同時に起こっているこ之を明らかにした。次にポリエステルエナメル線を試作し, 焼付け温度およびポリエステルの官能基度と電線のたわみ性, 耐ヒートショック性, 耐摩耗性, 耐熱軟化性, キュア速度および耐溶剤性との関係について考察を加えた。

Thermal Endurance of Enameled Wires Using Twisted Wire Specimens Statistical Analysis of Test Results

Thermal endurance tests to AIEE No. 571 were performed in six laboratories employing varnished specimens prepared in one laboratory with enameled wire from a single source. The results have been analyzed to test the hypothesis of the departure from linearity of the relationship between the logarithm of life and the inverse of the absolute temperature, with the object of subsequent limited extrapolation. Consideration is given to the variation between the results of different laboratories, and to reducing testing time. Comparison is made with previous AIEE results. Detailed numerical results are given.

Pigmented polyester magnet wire for high-temperature operation

This work was done to develop a conductor insulation with good space factor and winding properties, capable of operating at 1,000 degrees Fahrenheit (538 degrees centigrade). A flexible, clean-burning polyester resin was used as a binder for a glass frit and a refractory in a wire enamel composition. The polyester resin contributes sufficient flexibility to the enamel to wind it into equipment. After completion of the winding operation, the organic portion of the magnet wires is burned out and the glass frit is fused to bind the refractory. The resulting insulation is not a continuous film, and air breakdown values are obtained.

Aging of wire enamels in transformer oil

THERMAL aging characteristics of wire enamels aged under conditions similar to those which may be expected in sealed liquid-filled transformers have been studied and found to be quite different from results obtained by aging the same enamels in air. Enamels which have shown only fair thermal aging characteristics in air in comparison to other enamels may rate very differently when aged in a sealed system with a limited amount of oxygen present. For example, Formex (General Electric registered trademark) wire enamel which has a short life in comparison to a terephthalate polyester when aged thermally in a circulating air oven is equal or superior to the terephthalate polyester when aged in a closed system under oil.

Study of Thermal Deterioration of Enameled Wires by the Mass Spectrometer Method

Study of Thermal Deterioration of Enameled Wires by the Mass Spectrometer Method

The evaluation of enamel magnet wire

This paper is a discussion of the need to broaden the base of test procedures relating to enameled magnet wires. At present, the AIEE Publication no. 57, revised in 1959, establishes a method for determining the relative life of enameled wires as a function of thermal stability.1 Also available to air evaluation are the AIEE test procedures 65, 510, and 511.2 These are intended for evaluation of systems of which magnet wire insulations are an integral part. Experience is showing the desirability of providing acceptable test procedures for determining the relative life and the practicability or suitability of magnet wires as functions of other characteristics. Of importance, in this respect, are: 1. compatibility of the wire enamels with other substances, both of insulating function and environmental in nature, which are present in a complete electrical system, 2. thermoplastic flow properties, 3. heat shock characteristics, 4. change of reaction rate of aging properties with increase in temperature, 5. heat softening after extended aging, 6. retention of flexibility after aging, and 7. winding problems reflected in abrasion resistance, flexibility, reaction to rapid elongation, etc.

Elongation as a Factor in Evaluating the Thermal Stability of Enameled Wire

Examples are presented in which elongation exhibits an adverse affect on the shelf aging, thermal aging, and varnish-shock resistance of enameled wire. Methods for determining heat-shock and varnish-shock on enameled rectangular wire are presented. A consideration of the factor of elongation is important in the development of rectangular wire enamels, and it is suggested that elongation be considered as an addition to AIEE Publication no. 57.1