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How could a pulse cap operate in TC?



Original poster: Grishka <ghome@xxxxxxxxx>

Hello everybody,
The capacitor is the most critical part in a SGTC, because it should withstand
great power levels at rather high frequencies. Many factors are involved here -
maximum speed of voltage increase - i. e. dV/dt, dielectric loses in a cap,
level of its reactive power & some others. Many people doing rather nicy TCs are
completely careless in choosing right capacitor (MMC) and its parameters in operation.
I`ve seen many coilers using MMC and saying that "it`s working - so it`s OK". But
even using a MMC we should calculate some very important details.
I remember Terry Fritz wrote here:


http://www.pupman.com/listarchives/2002/July/msg01473.html

"MMC caps have a giant advantage in that they are cheap and easy to test under "deadly" conditions to
determine exactly how "much they can take". Expensive commercial caps can't be tested with such wild
abandon and we have to trust the typically "scarce" information the manufactures give us."


What is this "information"? What exactly parameters are the most criticle and important
for us? Now I`ve got a question about types of caps you use - reading some articles I found
the Maxwell caps to be the most reliable - if I`m not mistaken they were designed to operate
at laser applications. In such applications capacitor works in a pulse way with fast discharge
into low-resistance load with frequencies not more than 100..200 Hz.


Now questions:

-How could a Maxwell cap work in a TC, where frequencies are hundreds of KHz?
-Does it overheat a lot? What are the practical values for the dielectric loses in your caps?


Maybe people, who works with high-power RF applications can give some advices about using capacitors
in these devices?





-- Best regards, Grishka mailto:ghome@xxxxxxxxx