according to the actual design of the circuit, we choose the right high-voltage capacitor product. this is what every one of our technicians is doing. however, sometimes it may be caused by some components, which may cause problems in use. there are often two reasons for problems: either the wrong selection or the wrong product.
a high-tech communication equipment manufacturer purchased a number of high-voltage ceramic capacitors of type mzc-ct81-30kv-d32-502m from our company last month. during the process of use, the product's defect rate was found to be as high as 50% or more! such a high defect rate appears on a mature product, which is almost impossible. for this reason, our production personnel, quality control personnel, r&d personnel, etc. are all nervous: the problem lies in the end. where?
the defective products sent back by the customer are indeed in front of us: fried. is there a problem with the capacitor?
the sales team's salesmen individually called the customers who purchased the same batch of high-voltage ceramic capacitor products. what is the usage after receiving the goods? everyone's reaction is the same: the effect is very good, the quality is very reliable! finally, a bad report came from a customer in guangxi: there is a bad product!
everyone was relieved: all the high-voltage power boards were fine. all the x-ray machines were working properly. it was only because of a defective product from the customer in guangxi that it could not be verified that the capacitor was a problem. therefore, the root of the problem is to find the answer from the customer's engineer!
the customer feedback is as follows:
power frequency 50hz use; (obviously this is normal, nothing wrong!)
ac working voltage: 11kvac; (this is also acceptable, because our product's voltage withstand capability is more than 11kvac)
10 high-voltage capacitors are used in parallel; (use in parallel, that is to say only one stage in total, not boost circuit, this stage has to withstand 11kvac;)
pulse voltage: 2~3 times or more, the details are unknown, the customer can't provide it; (obviously, under this condition, the capacitor may burn out instantly, and it is no problem to withstand 11kvac, when it has to withstand 30kvac or above, definitely the moment is broken, because our capacitor is rated voltage 30kvdc ;)
as can be seen from the above, this capacitor is working under overload voltage. the overload voltage has its life.
then, let's analyze again, the customer's reaction originally used 30kv500pf capacitor, no problem in use:
first of all, in terms of the materials we use, 30kv500pf is the material of y5t, and 30kv5000pf is also the material of y5t; therefore, there is no problem that the material can't work;
secondly, we have to analyze why the same material, 500pf line, 5000pf can not. y5t is a material with good stability, but this material has a characteristic: although its voltage performance is very good, but the larger the capacity, the worse the pulse voltage withstand capability, so the two capacitors of 500pf and 5000pf are it is the same material, but the electrical resistance is different.
again, how good are the electrical resistance of the 30kv500pf and 30kv5000pf capacitors? the rated voltage of 30kv500pf is 30kvdc, and its breakdown voltage is above 60kvdc. it is no problem. according to the test, it is actually around 74kvdc. however, the breakdown voltage of the 30kv5000pf we have recorded so far is about 55kvdc. therefore, in this comparison, we know why the 500pf can be used, and the 5000pf has a problem.
in response to this problem, we recommend that the guest originally used 500pf 30kv, can use 1000pf 30kv, but it is not recommended to use 5000pf 30kv. because 1000pf 30kv can withstand voltages above 60kvdc, it is no problem to replace 500pf.
for more technical exchanges, please contact me: he pengfei 13549300303, or send an email: [email protected]
so why is this problem occurring? in the end, empiricism is at work. most of our customers use 30kv502m series voltage doubler to achieve the purpose of high voltage (high voltage generator), and this customer is different. he is not connected in series, but in parallel. therefore, our business staff recommended to the customer without asking clearly: use this! after many customer verification, no problem! the result is a problem.