As we all know, the current high-voltage ceramic capacitors are excellent in terms of capacity, voltage, loss, high-frequency characteristics, etc., only N4700 media. However, domestic and foreign manufacturers have broken their heads, and can not think of more attractive than the N4700. High-voltage ceramic capacitor products. Because the N4700 products are good, but they are fatal: the temperature change rate is too big!
Temperature change rate, bias characteristics, loss tangent, partial discharge, AC and DC withstand voltage, these are the necessary conditions for capacitive transformers, and all must meet the standard. Among all the materials, the most outstanding one is the N4700. However, this kind of medium that people love to hate, but people have to give up! The temperature drift of the N4700 has reached +30%. There is a considerable distance from the transformer required less than 5%.
Then, you can use better materials than the N4700, for example, N470, N750. or N150, NP0.
Things are not that simple. For example, N470, the temperature change rate is very suitable. But the dielectric constant is small. If you design a 50KV capacitor, the maximum capacity is only 300PF. The diameter is 60MM, the thickness is 32MM. It will be used in the 10KVAC circuit. How? Because the capacity is too small, the accuracy of the super-compositor is extremely poor. Even if the anti-interference measures are done very well, it may still strongly affect its accuracy. Therefore, in the transformer, the capacity requirement of the capacitor is not less than 1000PF.
It can be seen that the medium that is worse than the N470 will encounter the same unsatisfactory effect of the N4700 because the rate of change is not up to standard. The material with better quality than the N470 has a smaller capacity.
The key to solving this problem lies in the choice of medium. If blindly limited to the choice of ceramic media, there may be a road to nowhere. In this regard, Meishi capacitors adopt a newer way: silicide plus ceramics The medium, a new kind of ceramic material, not only can the capacitance be very large, the voltage can be very high, and the temperature change rate is no problem. At present, the sprinting stage, now more than a dozen doctoral tutors are fully adjusting the loss of the capacitor. The angle and the partiality are too bad. Once solved, this new capacitor is done!