RE: Marx Generator / Resistor Voltages (fwd)

[Steven Roys <sroys@xxxxxxxx>]

---------- Forwarded message ----------
Date: Thu, 04 Sep 2003 11:39:36 -0400
From: "Mccauley, Daniel H" <daniel.h.mccauley@xxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: RE: Marx Generator / Resistor Voltages



> >You don't need such a resistor if you are using them between
> stages.  I
> >use 1Meg, 600V, 3W carbon resistors with zero problems and
> I'm charging
> >my stages up to 40kV each.
> >Unless your charging current is super higher, you will never
> drop more
> >than a few hundred volts between each stage.
>
> But they will see the full stage voltage when the marx
> discharges, and I would imagine a 600V
> resistor run at 40KV may well deteriorate over time.
>
> >Dan

Actually no.  When the Marx Generator discharges, the capacitors look
like an extremely low impedance compared to the
very large impedance of the resistor paths.  Almost all current will
flow through the series capacitance path and very little voltage will
develop across the resistors (unless you are using very poor capacitors)
At the initial firing, there will be a very brief 40kv spike on the
resistor, but carbon resistors are very tolerant to these brief
transient spikes.  Metal oxide type resistors are much much less
tolerant.

I've already have probably > 10,000 pulses on my marx generator and not
one resistor failure yet.

Dan