[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Capacitor Help Needed



Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>

Hi,

guys - why do you use 942C20P15K? it`s more than 2 times worse in
C*U/$ than 942C16P68K for example, it has smaller peak & rms current.
i know that dU/dt is almost 3 times higher, but for 100-200 khz coils
942C16P68K should be fine, and then we just can increase number of
caps per string.

Let's see... For a 15/60 NST in the LTR mode we want:

http://hot-streamer.com/temp/MMCcapSales.gif

http://catalog.rell.com/scripts/SkuPage.asp?SKU=162589

27.3nF 22kV which is two strings of 11 of the 150nF caps. At $2.45 each that is $53.90.

From the data sheet:

http://www.cornell-dubilier.com/film/9422000.htm

864 amps peak and 27 amps RMS.

Now for the 942C16P68K

http://catalog.rell.com/scripts/SkuPage.asp?SKU=165330

$4.15 Each

http://www.cornell-dubilier.com/film/9421600.htm

680nF  1600V  781 amps peak  16 amps RMS

To get 27.3nF we would need to put 25 in series which would give use 25 x 1600 = 40kV The cost would be 25 x 4.15 = $103.75..

To get 22kV like we want, we would need 14 caps. 14 x 27.3nF = 382.2nF/cap... We could try the 942C16P33K at 330nF and use 12 caps to get to 27.3nF. The little extra voltage will not hurt them. So we need 12 of the 942C16P33K caps:

http://catalog.rell.com/scripts/SkuPage.asp?SKU=159547

$2.52 x 12 = $30.24 :-)))

We have to buy 27 of them though at $68.00 but maybe we could sell the extras here on the list ;-) They are back ordered, but Rell gets them in about a week. The peak current is 633 amps and the RMS current is 13.3 amps. We loose a good amount on the RMS current... "maybe" that is ok...

So If one shops around you might save some money. We like the 942C20P15K since it is one nice cap that we can order in giant quantities to get big discounts. But there are certainly other possibilites...

The Geek Group was also selling the 100nF 2000V caps since they matched many situations better for NSTs...

Cheers,

        Terry