1、 Insulation matrix: alumina ceramic matrix is usually used as the insulator for wire wound resistance, real ceramic rod is generally used for low-power wire wound resistance, and hollow insulating rod is generally used for high-power insulation matrix. The quality difference of rod body will have a great impact on the heat dissipation performance and performance of resistance.
American manufacturers generally use slightly gray ceramic tubes, while China and some Europe generally use white ceramic tubes. The gray ceramic tubes are slightly lighter, and the product performance indexes of the same quality grade are basically the same.
The low-power solid ceramic rod has strong anti vibration and relatively stable quality in the sintering process. The matrix of hollow ceramic tube used for high power is easy to break during transportation, and the poor quality ceramic tube is easy to crack during resistance sintering process. When the finished high-power ceramic pipeline is wound, sometimes the internal cracks caused during transportation can not be judged by the naked eye. Therefore, during the selection of ceramic tubes, high-quality ceramic tubes must be used to ensure consistency, good high temperature characteristics and stability.2、Resistance wire: the difference of resistance wire directly determines the temperature drift and resistance value of resistance, and also affects the short-term overload capacity of resistance and the long-term stability of resistance value. Nickel chromium alloy is the most commonly used wire rod, but the quality of each wire rod supplier and the composition of essential elements in thousands of poor gold are also different. The electrical properties of high-quality wire rod change little and the quality is stable during high-temperature sintering. The range of resistance values obtained by winding different grades of wires with the same size substrate is very different. This means that for equal power wire winding, domestic manufacturers can only achieve the kiloohm level, and foreign manufacturers can achieve hundreds of kiloohm or even resistance values. Different wire numbers need to be selected for different powers
3、Packaging materials: generally, there are eight kinds of insulating paints: insulating paint, silicone paint, mixed materials, plastic packaging, ceramics and aluminum shell. They are the most economical packaging materials. They are simple. They only need to be coated on the wound substrate. After low-temperature drying, the insulation performance is general, and they have little effect on the heat dissipation of the resistance. Therefore, the winding resistance coated with insulating paint is generally lower than the working temperature ˉ It is not suitable for applications with high temperature and high reliability requirements
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