JAVAMMC v1.06 Was: CD 942 failure tonight

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

Original poster: Bart Anderson <classi6-at-classictesla-dot-com> 

Hi All,

There is an obvious division of thoughts regarding MMC reliability when it 
comes to stand-off voltage. Some folks run near Vp or only slightly over 
and feel safe and confident with their cap banks. Others don't feel so 
confident and choose to derate their cap banks as they would any other high 
energy pulse cap. I personally am with the crowd who derates their caps in 
order to have that "confident feeling".

Anyway, I'm not posting to start a debate, but simply to let you know I've 
updated JAVAMMC to clarify the "reliability" terms.

I've added both "Temp Rise" reliability and "Cap Bank Stand-Off Voltage" 
reliability ratings as I view them. You can choose to set your own 
reliability as you see fit.

Here is how JAVAMMC determines reliability:
(view with fixed width font):

Reliability:        Cap Bank Voltage         Cap Temp Rise

   Excellent:           Over 2.5 x Vp           Less than 2
        Good:  Between 2 and 2.5 x Vp       Between 2 and 5
        Fair:  Between 1.5 and 2 x Vp       Between 5 and 8
Questionable:  Between 1 and 1.5 x Vp      Between 8 and 11
    Terrible:        Less than 1 x Vp       Greater than 11

Note, these ratings are tighter than what you might be use to, at least 
when it comes to rms. current and cap dissipation factors. JAVAMMC shows 
the above table as a reference. If you disagree with the above table, you 
can always ignore it.

http://www.classictesla-dot-com/java/javammc/javammc.html


Here's some of the output for John's recent MMC as based off this updated 
version:

J A V A M M C v.1.06 - CONSOLIDATED OUTPUT
Monday, March 01, 2004 12:00:10 AM
----------------------------------------------------
0.0667 [uF] = Cap Bank Total Capacitance
0.0167 [uF] = Capacitance Per String
4 [strings] = Number of Strings Required
36 [caps] = Total Number of Caps Required
Questionable = Reliability: Cap Bank Standoff Voltage
Fair = Reliability: Cap Temperature Rise
18000 [volts] = Cap Bank Rated Voltage
9.6 [joules] = Cap Bank Discharge Energy
1152 [watts] = Cap Bank Nominal Power
16971 [volts] = Transformer Peak Voltage
0.0015 [TANd] = Dielectric Loss Factor
0.2667 [joules] = Single Cap Discharge Energy
0.0096 [ohms] = Single Cap Internal Resistance
0.3057 [watts] = Single Cap Power Dissipation
6.726 [C°] = Single Cap Temperature Rise
22.52 [amps] = Capacitor String RMS Current

I know the cause of John's recent CD 942 cap failure isn't yet confirmed, 
but when you couple a "questionable" voltage rating with a "fair" temp rise 
factor, and add the fact that .0667uF is certainly larger than the majority 
of MMC users are running, I think it is reasonable to better identify cap 
reliability. Although his failure "sounds" like overvolting, the high temps 
may aggravate the standoff voltage ability and John has certainly 
identified a fair amount of heat involved.

Anyway, my concerns kept poking at me to better clarify this area. Thus, 
the updated JAVAMMC v1.06.

Take care,
Bart