Re: More on Coax Cables for High Voltage, and Connectors (fwd)

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---------- Forwarded message ----------
Date: Wed, 17 Nov 2004 20:12:41 -0800
From: Jim Lux <jimlux@xxxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: More on Coax Cables for High Voltage, and Connectors (fwd)

>
> ---------- Forwarded message ----------
> Date: Thu, 18 Nov 2004 09:39:23 +1100
> From: Tom Luttrell PWRCOM <tom@xxxxxxxxxxxxx>
> To: High Voltage list <hvlist@xxxxxxxxxx>
> Subject: RE: More on Coax Cables for High Voltage, and Connectors (fwd)
>
> This list http://www.webclot.com/high_volt/coax.xls indicates 4kVrms max
> for RG8.
>
> 4kVrms = 11.3kVp-p.


But the maximum magnitude at any given time is half that. PP includes the
polarity change, but the stress doesn't care about polarity (to a first
order).

In reality, the coax is rated to 10kV breakdown (generally, for RF cables,
you design for a worst case situation where you have a reflected wave of the
same magnitude as the forward wave.. so, the voltage would be double).

Then, the coax will actually take a lot more, because the mfr puts in a fair
margin to make SURE it won't breakdown at the test voltage (i.e. 10kV).
However, bear in mind that small voids (inevitable) and AC mean that the
voids will gradually get better, and eventually it WILL breakdown. It might
take years of constant voltage though.