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Re: MMC corona
Original poster: "Trent Mullins by way of Terry Fritz <twftesla-at-uswest-dot-net>" <neontrent-at-earthlink-dot-net>
Thanks for the experiment.
For the benefit of the rest of you, I recently had some terminal to terminal
arcing on my new MMC.
It can viewed at: http://hot-streamer-dot-com/TeslaCoils/MMCInfo/TrentMMC/
There are 3 strings per perfboard. While using 2 of the 3 strings, I had
arcing inside the box
from brass terminal to terminal. The arcing was between the 2nd active
string and the 3rd inactive string right along the plexiglas box on the
inside. Terry thought that maybe a static charge was building up inside the
So, I grounded the box and have since had NO problems :-)) The terminal
to terminal distance is 1 5/16".
Thanks again Terry,
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
Sent: Thursday, December 14, 2000 8:37 PM
Subject: MMC corona
| Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>
| Hi All,
| While working on an experimental MMC, I hooked the Bertran directly across
| two strings and charged the string ends to 24kV. With my Olympus 3000
| digital camera I was able to take a pretty good picture of the corona
| between the strings:
| This discharge starts at around 17kV and just gets worse as the voltage is
| raised until it arcs over at about 25kV. The terminals are 1.5 inches
| apart center to center.
| With a 15kV NST, the voltage between a dead and live string (this MMC is
| specifically made to have selectable strings) would be only 11kV peak AC.
| So It is probably ok but I thought I would share this info.
| Since it is really hard to solder up an MMC with ball solder joints to
| resist corona, there is probably a voltage level (~30kV) where streamers
| will start to propagate or arcing will make an MMC impractical. Thus if
| one were to try and make an MMC for say a 50kV transformer, it would need
| to be submersed in oil or something to stop this corona and the inevitable
| destruction it would do at very high voltages regardless of the number of
| caps per string.
| I should also mention that this was done at DC and the charging of the
| lexan and me was significant. I could get steady 1/8 inch arcs about once
| a second from my finger to a grounded object. Some serious fields are
| present! Also the negative side started corona much earlier than the
| positive as expected.
| A person had a problem with terminal to terminal arcing and this
| does not show any unusual problem. However, perhaps my 1.5 inch spacing
| greater than in his case?