How to select high voltage resistor

Recently, some customers have been consulting about the selection of high-voltage and high-resistance resistors. We have specially sorted out the precautions for selecting high-voltage resistors. Please pay special attention to the following items when selecting:
1. Selection of packaging materials for high-voltage resistors?
High-voltage resistors are used in power systems such as resistive transformers, and often require secondary potting. The surface of the resistor package must be smooth and must match the material of the secondary potting, otherwise tiny gaps may form between the surface of the resistor and the potting material. These tiny gaps will form local discharges under high-voltage environments, thereby carbonizing the packaging material. High-voltage resistors using high-grade epoxy resin encapsulation are significantly better than traditional silicone resin encapsulation, which can avoid the local discharge phenomenon caused by secondary encapsulation and enhance the reliability and stability of the high-voltage system. Before potting, we recommend cleaning the surface of the high-voltage resistor, and applying a surfactant is conducive to a more perfect combination of the potting material and the resistor surface.
2. Selection of high-voltage resistor accuracy?
In the design process of resistive voltage transformers, a thick-film high-voltage resistor and a fine-tuning potentiometer are generally used to complete the voltage division. The accuracy of the voltage division ratio can be adjusted by adjusting the fine-tuning potentiometer. This design can use high-voltage resistors with 1%, 2% or 5% accuracy. The highest level of fine-tuning potentiometers currently are foil technology fine-tuning potentiometers, which have low temperature coefficients and good long-term stability. When using two resistors to complete voltage division, it is necessary to select appropriate absolute accuracy and matching accuracy according to the requirements of the voltage division ratio accuracy. Matching accuracy is more important.
3. Choice of high-voltage resistor temperature drift?
In the application of voltage division, the ideal situation is that the temperature drift of the two resistors is consistent, that is, when the temperature changes, the resistance value of the resistor can change in the same direction, so that the voltage division ratio remains unchanged. Such a voltage-dividing resistor is called a voltage-dividing resistor with good tracking temperature drift. Generally, good tracking temperature drift can only be achieved after matching. Another method is to select two resistors with very low absolute temperature drift for voltage division, but resistors with very low absolute temperature drift are usually very expensive.
4. The relationship between the resistance accuracy and voltage of high-voltage resistors
The mainstream high-voltage resistors are all thick-film processes. The resistance of thick-film process resistors will change in a high-voltage environment. This is because thick-film resistors are a mixture of conductive and non-conductive materials. In a high-voltage environment, the non-conductive medium is activated to form a parallel resistor, so that the resistance of the resistor changes in a small direction as the voltage increases. The low voltage coefficient is determined by the slurry level and manufacturing process of the resistor.
5. While pursuing high precision, pay attention to the stability of the resistance value of the resistor
High precision without stability is meaningless, because the resistance value of the resistor will change during storage or load, and this change is irreversible. When selecting a resistor, these changes must be taken into account to ensure that this change is within the allowable range of measurement accuracy. Kaibu Electronics' high-voltage resistors are all tested for high voltage before leaving the factory. This test helps to stabilize the resistance value of the resistor.
6. It is very important that the performance of the resistor is stable and reliable when working
The design life of the equipment puts forward requirements for the reliability of the resistor. In the high-voltage switch system, the resistor is not allowed to fail, so a high-voltage resistor with reliability indicators must be selected and necessary derating must be performed. Shenzhen Star Electronic Technology's high-voltage resistors have more than twenty years of experience in related applications in high-voltage switch systems, and their failure rates exceed military standard requirements.