定义:definition:
The voltage divider mainly has a resistive voltage divider, a capacitive voltage divider, and a resistor-capacitor voltage divider. The voltage divider capacitor here refers to the core material of the capacitor voltage divider [1] in high-voltage power equipment: High temperature arm and low voltage arm capacitors with the same temperature characteristics and high voltage AC characteristics.
Dielectric material:
The voltage divider capacitor must guarantee a large premise that the temperature change rate of the high voltage arm and the low voltage arm is the same. The best way to preserve this characteristic is to use the same dielectric material for the high voltage side and low voltage side capacitors. To ensure the temperature change rate, and to ensure the high voltage and partial discharge characteristics on the high voltage side, it is undoubtedly more difficult to select the capacitor material. Because the high voltage side often has to use ceramic materials with lower dielectric constant, and the low voltage side lacks the required pole. High capacity, which is contrary to the above, usually can not meet these two conditions at the same time.
GC ceramic media is such a ceramic dielectric material that satisfies multiple conditions. This medium has high withstand voltage characteristics, and its temperature change rate is extremely small, ranging from -40 degrees to +125 degrees. Guaranteed within 3%. Therefore, researchers have made this material the best choice. At least at the current level of technology, there is no better material to choose from.
性能:performance:
The biggest feature of GC ceramic materials is the extremely high withstand voltage and low temperature change rate and slight partial discharge.
This kind of medium can withstand 20KV DC withstand voltage per 1MM. Only 7mm thickness chip can withstand 45KVAC voltage test, pulse voltage capability is higher than 75KV, it is completely feasible to operate in 10KVAC equipment.
The rate of temperature change has always been a defect of ceramics. Compared with metallized films, the temperature change rate of ceramic materials is higher. The appearance of GC materials directly negates this traditional view. Because at 0-50 degrees, The temperature change rate of this kind of GC ceramic capacitor [3] is basically within 0.5%. The range of -40 degrees to +125 degrees, the temperature change rate of this kind of GC capacitor is also controlled within 3%.
The GC ceramic medium is casted instead of the die-casting method of the general ceramic capacitor. Therefore, another advantage of the GC capacitor is its advantage in partial discharge. The partial discharge is difficult to control in the die-casting sintering process, and the GC capacitor is easy to Solved. Because the density of the GC medium is quite good, it can be regarded as 100% dense. Therefore, the local discharge electrode is weak. This is also the reason why the used technicians like it very much. The partial discharge of the ceramic capacitor is usually larger. .
Advantage
The use of GC ceramic capacitors, in addition to the above-mentioned performance advantages, also has a trait: in theory, the voltage of such GC ceramic capacitors can be infinitely large, and the capacity can be infinitely high. Therefore, engineering researchers have thought of using this GC ceramics are used at both ends of the capacitor of the voltage divider. Because this material can meet the high and low pressure side while using a medium, and the capacity ratio can be as high as 50 times or more than 100 times - if the size is not limited, It can reach several hundred times.
Usually we use the 100PF40KV GC capacitor as the capacitor for the high voltage arm. This capacitor is characterized by: rated voltage of 10KVAC for working operation, 45KVAC for AC test voltage, no problem for 5 minutes. Impact voltage for 75 minutes OK. Capacitor for low voltage arm. 2KV5000PF or 2KV10000PF. Also use the same system of GC medium to ensure the same temperature change rate.
Shortcomings
The ceramic capacitor of GC medium has various advantages, but it inevitably has an unacceptable disadvantage: the size is too large. In the case of a 40KV1000PF GC capacitor, the finished product size reaches 60mm in diameter. The diameter of the N4700 ceramic capacitor is Only about 45MM. This gap can not be accepted in many strict size equipment. In terms of the characteristics of GC medium, the production of 2N to 50NF high-voltage capacitors is perfect, but its size is basically useless. Imagine a 40KV10000PF capacitor, although it is excellent in terms of AC and PD, but the diameter is about 115MM. Who can accept this size?
Therefore, GC is a very good dielectric ceramic material, but there is still a large improvement and improvement space. How to solve the size problem is the primary problem.
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