Re: Are these TDK HV Capacitors any good ? ? ?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Bert Hickman by way of Terry Fritz <teslalist-at-qwest-dot-net>" <bert.hickman-at-aquila-dot-net>

Steve and all,

The specs for both the UHV and FHV series capacitors can be seen/downloaded 
at TDK's Japanese site:
http://www.tdk.co.jp/tefe02/e4E38_UHV_FHV.pdf

Actually, both of these series use strontium titanate as the base 
dielectric, and both have the same dielectric loss (0.2%). The only 
difference is that the FHV series uses a slightly different dielectric 
formulation that gives it a lower negative temperature coefficient. 
Otherwise, both types should perform well in pulse discharge, and even 
Tesla Coil use, as long as they are not overstressed.

While neither of these are true RF ceramic capacitors, they can be made to 
work in some RF applications. However, I certainly wouldn't design them 
into the tank circuit of a high power VTTC. As Scott indicated, use mica 
caps transmitting instead - they can take the heat, the dielectric is 
virtually immune to corona damage, mica has a much lower temperature 
coefficient, and they come with stamped RF RMS current ratings. And it's 
what the pros use (along with vacuum capacitors) in commercial broadcast 
equipment.

Best regards,

-- Bert --
-- 
-------------------------------------------------
Where Small Change is created "Electromagically"
Coin crushing by powerful electromagnetic fields
Stoneridge Engineering: http://www.teslamania-dot-com
-------------------------------------------------

Tesla list wrote:
>Original poster: "Steven Ward by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
><srward16-at-hotmail-dot-com>
>Hello,
>I thought that it was stated that Strontium Titanate was ok for RF use???
>And that Barium Titanate (the cheaper stuff) was not as good, and was only 
>useful for DC or NST filters?  I personally have used the UHV-9A 2000pf 
>40kv caps.  I use them in a series parallel to make a 2000pf 80kv bank (4 
>caps total).  The really dont experience any warming in this 
>configuration, but did during another test when i tried a lower frequency 
>tank circuit, and only used 2 caps in parallel.  I have often 
>seen(including myself) these caps used in spark gap coils with very good 
>performance.  I used 4 in parallel in a small 500W coil, and they ran for 
>very long periods, and experienced no heating or no change (or negligable) 
>in tuning.  My tube coil also does not seem to have a problem with them, 
>and i often run it for lengthy periods of time.  So i dunno, they have 
>worked well for me, even if not spec'd for it.
>So whats the deal on these things!?!?
>Steve Ward.
>
>
>>From: "Tesla list" <tesla-at-pupman-dot-com>
>>To: tesla-at-pupman-dot-com
>>Subject: Re: Are these TDK HV Capacitors any good  ? ? ?
>>Date: Tue, 25 Feb 2003 10:53:23 -0700
>>
>>Original poster: "Scott Hanson by way of Terry Fritz 
>><teslalist-at-qwest-dot-net>" <huil888-at-surfside-dot-net>
>>
>>Unfortunately, the TDK UHV series are DC capacitors with a rather high
>>temperature coefficient (Z5T). They are not for RF use. The dissipation
>>factor is quite high, at .2%, presumably at 1 kHz.
>>
>>TDK does make a similar series of HV ceramic capacitors (FD series) that are
>>rated for AC service, but I couldn't find any specific info on dissipation
>>factor. Although used in laser triggering applications, the rep rates are
>>relatively low compared to the RF frequencies used in Tesla coils.
>>
>>Stick with capacitors using polypropylene dielectric for spark-gap coils and
>>mica for VTTC's.
>>
>>Scott
>>----- Original Message -----
>>From: "Tesla list" <tesla-at-pupman-dot-com>
>>To: <tesla-at-pupman-dot-com>
>>Sent: Monday, February 24, 2003 7:49 PM
>>Subject: Are these TDK HV Capacitors any good ? ? ?
>>
>>
>> > Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>"
>><dhmccauley-at-spacecatlighting-dot-com>
>> >
>> > Just curious if these TDK capacitors are any good for VTTC and other types
>> > of tesla coils.
>> > I tried looking for a datasheet, but couldn't find one
>> >
>> > TDK, Type UHV-11A, 50kV, 1000pF
>> >
>> > If they are, there is a lot of 18 NEW ones going on sale at Ebay below
>> > starting at $95.00 and only one day left.  Be a great deal if they were
>>good
>> > caps!
>> >
>> >
>>http://cgi.ebay-dot-com/ws/eBayISAPI.dll?ViewItem&item=2510763356&ssPageName=MER
>> > C01
>> >
>> >
>> > The Captain
>> >
>> >
>
>.