[Prev][Next][Index][Thread]

RE: Bipolar Coil (was: Coiling Goals)

Terry/List,

Thanks! I'll update my paper.

Found a problem with one of the EMMC modules I was originally using (the
connection to the bus had come loose burning the brass screws and melting a
couple of the resistor connections loose). Everything looks fine now but a
lesson was learned. Do not trust the resistors as the primary safety
measure. Use them to enhance the safety margin.

As for the temperature. If you remember, you were originally concerned with
a possible drop in capacitance as the EMMC's were run hard (and were
possibly self-healing). My initial measurements (which were at the limits of
my meter) seemed to support your observations. I was able to see a slight
and repeatable reduction in "C" immediately after a hard run (500khz for
2-5min). This drop was in the 1-2% range and the caps were getting hot.
However, I did read consistent measurements without any reduction in
capacitance if I let them return to ambient temperature first. We may be
splitting hairs here since the difference was tiny and at the limits of my
test equipment.

Regards,
Brian Basura



-----Original Message-----
From: Tesla List [mailto:tesla-at-pupman-dot-com]
Sent: Sunday, December 26, 1999 12:24 PM
To: tesla-at-pupman-dot-com
Subject: re: Bipolar Coil (was: Coiling Goals)


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

Hi Brian,

	Your white paper on your mini twin coil is super nice!!  Extremely
well
written and informative.  There were two things that caught my eye.

In the middle of the first page, you talk of the EMMC with the 10Meg
resistors and say "This EMMC module retains a noticeable charge for at
least 30 seconds."  However, The EMMC should be virtually discharged in
only 5 seconds?  If one charges a 0.056 cap to 20,000 volts and then
discharges it with a 10Meg resistor, the voltage will fall from 20kV to
2.59 volts in 5 seconds.  I don't see how it could be shocking you after 30
seconds.  Perhaps it is static charge or something.  If the cap is not
discharging very quickly, we should probably figure out why.  A lot of
people use MMCs and if there is a problem with the discharge we should
probably figure it out ;-)  Is it possible that a cap does not have a
resistor across it or a resistor has failed open?

The second note was at the top of the second page where you say "It was
important to give the EMMC module time to return to ambient temperature
before making the (capacitance) measurement."  Poly caps should vary about
1% for every 20 degrees C (according to WIMA).  Does this seem about right
in your experience?  I was wondering if the capacitance was changeling any
more than expected due perhaps to our rather "enhanced" use?  It may be
possible that the value is drifting temporarily due to the high voltage,
current, frequency stress and then that stress relaxes and the value
returns to normal.  I was just wondering if you had noticed anything we
should be concerned about for EMMC design.

I did a little experiment.  I measured my EMMC at 27.7nF at the room
temperature of 19.7 degrees C.  Then I took it outside and let it cool down
to arctic Colorado temperatures of 13.2C (it was 17C here on Christmas day,
Santa needed a short sleeve shirt ;-))  The capacitance still measured
27.7nF.  I have it in the refrigerator now...

Cheers,

	Terry


At 10:55 AM 12/24/1999 -0800, you wrote:
>Ralph and others,
>
>Check out the "Mini-Twin" schematics and white paper located at
>http://fp2.hughes-dot-net/brianb/newpage12.htm 
>
>I'll answer any questions (that I can that is).
>
>Happy Holidays,
>Brian Basura
>
>
>
>-----Original Message-----
>From: Tesla List [mailto:tesla-at-pupman-dot-com]
>Sent: Thursday, December 23, 1999 10:39 AM
>To: tesla-at-pupman-dot-com
>Subject: Re: Coiling Goals
>
>
>Original Poster: Parpp807-at-aol-dot-com 
>
>In a message dated 12/22/99 8:51:58 PM Central Standard Time, 
>tesla-at-pupman-dot-com writes:
>
><< The next goal was the design, documentation, construction and packaging
>of
> the "Mini-Twin" bipolar coil. This took a lot of perseverance to complete
> (to my satisfaction that is).
>  >
>
>Brian,
>
>There does not seem to be too much discussion or information re bipolar
TCs.
>Any info you care to give will be much appreciated and perhaps even used.
>
>Happy day,
>Ralph Zekelman
>