Re: Dont get zapped. ( safety shorting relays on HV ps outputs)

To: tesla-at-pupman-dot-com
Subject: Re: Dont get zapped. ( safety shorting relays on HV ps outputs)
From: "Harri Suomalainen" <haba-at-cc.hut.fi> (by way of Terry Fritz <terryf-at-verinet-dot-com>)
Date: Tue, 15 Sep 1998 16:37:04 -0600
Approved: terryf-at-verinet-dot-com

>Shorting the output is standard practice for most commercial HV
>equipment. You use a Normally Closed relay (often gravity is the force
>that closes it). Then, power coming through the interlocks, etc, is used
>to open the safety short. This is especially useful for systems with any
>stored energy (like output filter capacitors), because when you turn it
>off, the cap gets shorted. Actually, on one of my HV power supplies,
..
>I got tired of having the big bang everytime the power flickered and the
>saftey interlock dropped the short on the filter cap.

I used a similar thing to discharge some large electrolytic caps with one
solid state coil prototype. It allowed quick discharging (limited by a
resistor)
and made fast adjustments or modification possible.

Unfortunately, at the time,  I had assumed the resistor would take the
pulses
for long-term use. It did not. 350V/470uF charged cap gave a nice zap. :)
Make sure you have a resistor that will be able to take the pulses *and*
have an indicator or check the caps by shorting them with a suitable
object.
I learned not to rely on such a simple protector without a secundary
system.

I doupt anyone wants to make the mistake I did, at least not with hv
charged
caps!


--
Harri Suomalainen     mailto:haba-at-cc.hut.fi

We have phone numbers, why'd we need IP-numbers? - a person in a bus