Re: MMC corona

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

Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>

Hi Trent,

	Great to know the problem is solved!  However, I must ask, how in the
world did you "ground" the plexiglass box?

Cheers,

	Terry


At 09:26 PM 12/14/2000 -0700, you wrote:
>Terry,
>
>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
>box.
>
>So,  I grounded the box and have since had NO problems  :-))  The terminal
>to terminal distance is 1 5/16".
>
>Thanks again Terry,
>
>Trent Mullins
>
>
>----- Original Message -----
>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: <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:
>|
>| http://hot-streamer-dot-com/TeslaCoils/Misc/MMCglow.jpg
>|
>| 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
>experiment
>| does not show any unusual problem.  However, perhaps my 1.5 inch spacing
>is
>| greater than in his case?
>|
>| Cheers,
>|
>| Terry
>|
>|
>|
>|
>