Enamel Insulation Research Articles

Thermal properties of impregnating materials for stable superconducting magnets

The minimum quench energies (MQEs) of superconducting (SC) wires have been measured precisely by means of a 'Carbon Paste Heater'. The thermal behavior just before the normal generation of the heavy loaded SC wire was observed to determine the quenching. We learned that once a normal region is produced, it should spread rapidly regardless of the surrounding conditions. The MQE, however, would increase when a local temperature rise before quenching is prevented by using certain materials around the SC wire. For example, high thermal diffusivity in impregnating materials or low thermal conductivity in wire insulation will be needed when disturbances occur outside of the SC wires. In the previous paper, we showed the effects of enamel insulation for improving stability. Thus, in this study, we examine the relation between MQE and the thermal properties of the impregnating material. Several kinds of impregnating materials were selected and the thermal properties are compared with enlarging MQE in mind. We have searched for an impregnating material that has the thermal property required for improved stability.

樹脂含浸エナメル絶縁の高温ヒートサイクル劣化

樹脂含浸エナメル絶縁の高温ヒートサイクル劣化

Stripping poly-imide resin (Trimel) enamel insulation from fine wire to produce electromyography electrodes

Stripping poly-imide resin (Trimel) enamel insulation from fine wire to produce electromyography electrodes

A method for evaluation of thermal stability of magnet wire enamel

A method for evaluating the thermal stability of magnet wire enamel has been developed using the dielectric strength of the enamel film as a criterion. This test method was designed for accuracy, simplicity, and economy in time, labor, materials, and equipment. Standard National Electrical Manufacturers Association (NEMA) dielectric strength twists1 are dipped in an electrical impregnating varnish and used as test samples. To achieve sufficient accuracy, a large number of these twists are included in an enamel evaluation program. The twists are placed in aging ovens at various temperatures. Periodically the samples are removed and tested by applying a high voltage. The average aging time required to reduce the dielectric strength of the twists to a preselected value is considered the life of the enamel. The relative life of the enameled wire insulation system over a wide temperature range may then be predicted from the life of the samples determined at several temperatures. Studies have been made of this test method under different sample preparation methods, failure criteria, and aging conditions. Results determined by this test are compared with motor-aging test results on the same enamel-impregnating varnish insulation systems. This comparison shows that this is a convenient functional test method that can be correlated with the results of a more complicated motor test program.