Re: ASEA Caps

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Bert Hickman <bert.hickman@xxxxxxxxxx>

Tesla list wrote:
> Original poster: Justin Oliver <justin@xxxxxxxxxxxxxx>
> hi,
> a mate of mine has got me a few of these ASEA caps, type CT0A1/22, and i 
> was wondering if anyone knew if they are suitable for tesla coil work. ive 
> put a few photos up at http://img209.exs.cx/gal.php?g=caps3ba.jpg
> thanks,
> -j

Hi Justin,

The number on the upper right hand corner may indicate the year of 
manufacture (1963). The term "Discharge Device" may be a safety warning for 
linemen (PFC application) or it may indicate possible use in pulsed 
applications. If the latter, then these could indeed be low duty cycle 
pulse capacitors that were initially part of pulse forming networks (PFN's) 
built using early-1960's capacitor technology.

However, since the faceplate also says "50 Hz", these caps are most likely 
PFC caps used in the electrical power industry. Power transmission and 
distribution systems were also ASEA's primary line of business. The UpV 
rating of "22/V3KV" may be the surge (22kV peak?) and nominal (3KV RMS?) 
operating voltages for insulation coordination with HV protection devices 
(lightning arresters). The oversized insulator is typical of power factor 
correction caps since they must withstand many years of lightning surges 
and outside pollution. It is interesting that the KVAR rating has been left 
blank, however. And, at 0.34 KVAR (if 3 kV RMS), these would actually be 
pretty small PFC's. If they were rated for 22 kV, then they would be about 
15 KVAR (still small, but a more reasonable size for PFC use).

You could also try connecting an ohmmeter across one to see if they contain 
an internal bleeder resistor - if so, they are undoubtedly PFC caps. In any 
event, the dielectric system is quite likely paper-oil or possibly 
paper-Mylar-oil. They would predate polypropylene-paper-oil technology. 
There is also a very high probability that they contain PCB's. 
Unfortunately, the only way to know for sure is to contact ASEA (now Asea 
Brown Boveri Ltd. or ABB) to see if they can provide any information.

Or, you could carefully perform an autopsy on one of them. Once you've 
carefully taken one apart, you can then test the oil for PCB's (see the 
Pupman archives) as well as examining the internal construction and 
dielectric system. The internal construction will also provide you with 
clues to working voltage and suitability for higher frequency operation. 
BTW, paper-oil capacitors are actually quite robust for DC and LOW duty 
cycle pulsed power applications, particularly where there is significant 
voltage reversal (ringing). Many early magneforming machines actually used 
paper oil caps because they were more robust in the presence of high 
voltage reversals.

If these caps do contain PCB's you'll be taking on a long term 
responsibility for disposal ($ cost) that you really don't want or need. 
MMC caps are PCB- free, inexpensive, and most likely better performing, I'd 
suggest avoiding these ancient ASEA caps like the plague unless they can be 
proven to be PCB-free.

Best regards,

-- Bert --
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