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December 14, 2015

N4700 type high voltage ceramic capacitor can not be used in the instrument transformer?

1to8kv (2)


As we all know, the current high voltage ceramic capacitor, in capacity, voltage, loss, high frequency characteristics and other aspects are excellent, only N4700 medium. However, the domestic and foreign manufacturers have broken the head, also can't think of a more attractive than N4700 high voltage ceramic capacitor products, because N4700 capacitor product is good, but there are fatal injury: the temperature change rate is too large!


The temperature change rate, bias, loss tangent, partial discharge, AC and DC voltage, which is a necessary condition for capacitor transformer, the current must be standard. All of the materials, the most outstanding is N4700 for performance, but this one is not the medium people love and hate, but call the person had to give up! N4700 temperature reached about +30%. There is a considerable distance from less than 5% transformer requirements.


Well, you can choose to use a better material than N4700, such as N470, N750. or N150, NP0.


N470, the temperature change rate is very suitable, but the dielectric constant is smaller, if the design of a 50KV capacitor, the maximum capacity of only 300PF. diameter 60MM, thickness 10KVAC in the 32MM. circuit, due to capacity is too small, the accuracy of the transformer is very poor, even if the interference measures are very good, still may strongly affect its accuracy.


It can be seen that the medium is worse than N4700, because the change rate of the degree of N4700 is not satisfied with the effect of the same N470.
The key to solving this problem lies in the medium of choice. If blindly confined to the ceramic medium choice, may have no way out of the predicament. In this aspect, the HVC capacitor has taken a newer way: silicide with ceramic dielectric, generating a new ceramic material, not only can do capacity large voltage can be very high, the temperature change rate is also no problem. Now the sprint stage, now more than a dozen Ph.D.advisor loss angle is fully adjusting the capacitance and partial bad characteristics, once solved, the capacitance is done for the new!

 

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