Also back in the 60's I was an engineering tech for High Voltage
Engineering. The power supplies were 100-400KV at up to 300ma. All testing
was done behind a radiation and blast proof brick and steel door.
Failures were interesting to say the least and it also took many tries
before they got a reliable crowbar circuit.
They were also building a 1 megavolt supply for the government and that
pretty much took them down the tubes as it wasnt as easy as they thought
when bidding.
Carl
KM1H
----- Original Message -----
From: "Peter Chadwick" <g3rzp@g3rzp.wanadoo.co.uk>
To: <amps@contesting.com>
Sent: Tuesday, October 02, 2007 4:41 PM
Subject: [Amps] 8877 Grid Trip timing
> Back in the '60s, working on a sground sattion for satellites, I was, as
> an apprentice, involved in testing the crowbar on a 22kV 3Amp supply.
>
> We dumped a 24 microfarad capacitor through a 10 ohm resistor and
> ignitrons.
> Said resistor was a 'globar' type, 3 inches in diameter and 14 inches
> long. It was attached by straps of copper 3/16 thick to a fibre glass
> board 1/4inch thick. After some 250 discharges, there was an explosion,
> and the resistor disintegrated, with half of it departing through a 1/8
> inch thick pressphan sheet and going some 20 feet across the lab. I was
> a bit dubious when I could see sparks running across its surface.....
> I've been a bit dubious about crowbars ever since...
> 73
> Peter G3RZP
>
>
>
>
>
> ========================================
> Message Received: Oct 02 2007, 08:19 PM
> From: "Jim Tonne"
> To: "Karl-Arne MarkstrÃm" , amps@contesting.com
> Cc:
> Subject: Re: [Amps] 8877 Grid Trip timing
>
>
> Karl-Arne wrote in part:
>
>> . . . short circuit the 14 kV 15 A rectifier using a
>> 0,3 mm silver wire, which should not burn off or
>> melt. This obviously required some courage by
>> the maintenance personnel.
>
> That brought back a memory of my first exposure to
> crowbars (also using iggies).
>
> It was at Continental and it was a very long time ago.
> I had never heard of crowbars and they were getting
> me up to speed on the innards of high power as
> compared to lowpower [50 kW or less] which was
> my background to that time.
>
> My boss went around, telling everyone that I was
> about to learn how to test the crowbar. He told
> everyone in earshot to get their earplugs, or at least
> get ready to plug their ears. I think he winked at
> each of them but of course I didn't know that. He
> looked at me with a look of pity, poor boy, you
> can't hold the stick to do the shorting and also plug
> your ears so you'll just have to tolerate the noise.
>
> So I got up my courage at the right moment and
> shorted the high voltage. It silently tripped off. All
> the meters went to their standby readings. I guess
> the HV transformer kind of grunted. But not a
> sound excepting for LOTS of laughing about how
> they had got me all prepared for a huge mess and
> how nervous I ought to be.
>
> Clowns!
>
> - JimT
>
>
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