kvar

[Crusher]

I was wondering if anyone knew or could point me in the right direction. I have been looking at a lot of the russian surplus stock of capacitors. Usually they do not have a current rating. Just a voltage rating. Some will say 6 or even 90kvar. Is there any way to tell what the capacitor will handle current wise safely? By the writing on capacitor. Say for instance, 470pf @ 4kv @ 10kvar?

 

[fodendaf]

i dont know kvar but kva is another way of saying watts so 10/4=2.5 amperes perhaps?

 

[Crusher]

Kvar stands for Kilo Volt Amp Reactive. I wish it was easy as kva. But I don't think so. Power companies use kvar to find out if a commercial business has an inductive load and uses caps to get it close to in phase. But don't know how it works with these russian caps.

 

[Crusher]

Huh, nobody?

 

[fodendaf]

If you're still stuck you could make a post with google translate here: Два.ч — Радиотехника
It's a russian image board for radio techs. You don't need a user name or password, just fill in a captcha and you're all set.

 

[Captain Kilowatt]

Unless you are using the capacitors on the AC line to compensate for heavy reactive loads like commercial businesses do then just forget about the KVAR rating. It means nothing in normal situations like power supplies etc. If you REALLY want to know there is some good info in a couple threads here starting with this one.

CR4 - Thread: Capacitor value

 

[Crusher]

The reason I was asking, I see some nice sized doorknob caps that look like they would work great as a blocking capacitor for a tube amp. But question current rating.

 

[Shockwave]

I think I know the Russian caps you're talking about. Large diameter with blue paint covering the ends and three wide straps that sort of form a mini tripod to make the connections on each side? If that's the style than one will hold the current of tube you're building as long as you select one with at least twice the plate voltage rating. These should be about the diameter of a standard glass beer bottle but much shorter in height. It's the diameter of the plates that determines the current handling.

 

[Crusher]

I have some 470pf @ 20kv @ 60kvar capacitors. Rf parts sells them for $129 each. I paid a lot less for 4 some years back. I have used 1 on a 3cx3K box and it ran fine. They are the diameter and thickness of a hockey puck. They have a lot of weight to them. They have a screw on each side like a regular doorknob. I was just trying to figure out what they are really rated for than just guessing. I have seen 2 of them used on a 3cx10,000a7 amplifier awhile back.