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Re: ASEA Caps

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

Tesla list wrote:
Original poster: Justin Oliver <justin@xxxxxxxxxxxxxx>
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

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 --