Re: SISG MOT system ballasting question?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "S&JY" <youngsters@xxxxxxxxxxxxxxx>

Terry,

At some point, consider charging your MMC with a second string of SISG
modules.  Turn them off, then fire your other string of SISG modules to
discharge the MMC into your tank circuit.  It also completely disconnects
your power supply from the resonant circuit (except for the little bit of RF
that couples through the turned-off IGBTs).  And if you charge the MMC
through a charging reactor and dequeing diode string, you can start with a
lower DC voltage, and take advantage of the times 2 voltage multiplication.
And as a further bonus, the charging reactor is also a current limiter, so
your IGBTs in the charging circuit don't have to handle much current.  This
also completely avoids the need for ballasting your MOT(s).   The power is
completely controllable via DC voltage & BPS.

What I don't know is the effect of a turned-off string of IGBTs across the
primary circuit.  Certainly there would be some capacitance, but one could
lower the value of the MMC to compensate.  Are there other bad effects?

This scheme works wonderfully well with spark gaps (rotary).  I have never
succeeded in making it work with triggered spark gaps - couldn't prevent
both gaps from sporadically firing at the same time, which shorts out the
power supply, pegs meters, etc.  One would have to be very careful to ensure
the two strings of SISG IGBTs could not conduct at the same time.

--Steve Y.
----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Wednesday, May 17, 2006 7:53 PM
Subject: SISG MOT system ballasting question?


> Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>
>
> Hi,
>
> I have been working on collecting parts for the 280W SISG
> system.  Tons of parts come in tomorrow.
>
> But I am a little "stuck" on "how" to ballast the MOTs.  It is a dual
> MOT full bridge rectifier.  The MOTS charge a 150nF cap to 5600V at 120
BPS.
>
> http://hot-streamer.com/temp/SISG-MOT-System.gif
>
> My brain is sort of fried at this point and I never have played with
> ballasted systems before...  It is run off a variac so there is room
> to play...  I was going to model it and all, but fighting the models
> will take hours...  Maybe someone just knows the value of inductor or
> resistor it needs?  *:-))
>
> I got the "parts" to make anything...
>
> The SISG will fire at 5600 volts, so I need to recharge the 150nF cap
> at 120BPS for 282 watts of fun ;-)
>
> I was going to figure it out tomorrow morning but the county ran an
> earth mover into a fence...  So I will be in the mountains tomorrow
> stretching wire...
>
> Cheers,
>
> Terry
>
>
>
>
>