Plastic dielectric strength
thermal breakdown was due to electric field, under the action of medium temperature rising of breakdown phenomenon, using electrical equipment breakdown is often happened in the thermal breakdown. Dielectric strength can be used as a measure of insulators is an important index of the electric strength, dielectric strength is higher, the better the insulation quality. Dielectric strength and material properties, the shape of the material, contains impurities and the working condition such as temperature, humidity, mechanical stress and so on. The design should pay special attention to the actual working conditions.
in the switch, circuit breaker and switchboard a class of applications often prone to arc, arc resistance should choose good material. Plastic materials, some of the arc resistance is poorer, such as bakelite, others have very good arc resistance, such as melamine resin and ptfe. By adding inorganic filler, can greatly improve the plastic arc resistance. Leakage electricity traces and arc resistance are two different concepts.
usually homogeneous plastic dielectric strength is relatively high. It is important to note that the plastic data with the test method of breakdown strength varies with the condition of sample, general information provided by the data may come from the different testing methods, and thus cannot be directly compared, secondly data table for dielectric strength, tend to be achieved in a short period of time to make labor frequency electric field, therefore can only finalize the design of the surface of the conditional material's ability to withstand voltage, but not as the main basis of insulating material selection and design.
plastic high dielectric strength for a short period of time doesn't mean it can be applied to high voltage, also can't shows that he has a long-term high dielectric strength. Because of the lack of certain use environment for a long time enough data compression strength, so most need to rely on experience in design. Arc is through gas electric discharge phenomenon.
in the field of polymer injection molding processing, when the electric field intensity exceeds a critical value, become lost insulation performance, this phenomenon become a breakdown. Specimen was breakdown voltage and is defined as the ratio of dielectric strength. There are electric breakdown, thermal breakdown of dielectric breakdown, and several types, such as chemical breakdown but mainly electric breakdown and thermal breakdown. Electric breakdown is mainly caused by the voltage rising, occurrence breakdown of a relatively short time.
plastic material resist the ability of arc to near its surface, called arc resistance. Under the action of an electric arc is destruction features, material and local heat or burning, carbonized material surface, forming the so-called arc track, which is conductive channel. Therefore, often used the materials needed to form a conductive path time as the arc resistance index. Arc resistance of plastic material is an important performance index.
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