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From: "John Jardine"
Subject: Re: 12kV 8kW metal-evaporation power supply
Date: Sun, 17 Nov 2002 15:27:43 -0000
NNTP-Posting-Date: 17 Nov 2002 15:16:22 GMT
X-Newsreader: Microsoft Outlook Express 5.00.2615.200
Winfield Hill wrote in message
> A friend calls up and says his 12kV 8kW metal-evaporation power
> supply is on the skids. Seems the designers used six 250k 50W
> power resistors in series for two tasks: HV bleeder and the
> voltage-feedback servo path. A resistors goes, so the HV supply
> soars and becomes erratic. It's sad the decisions that engineers
> sometimes make. I have a nice foot-long 60 meg-ohm glass >25kV
> resistor that looks ideal for the task. Not to mention some nice
> 3-inch long parts. I also suggested an interlock set to operate
> if inadequate current is present in the bleeder chain. BTW, the
> company has since gone out of business.
> - Win
I was going to suggest that the 1.5Meg chain would be better distributed
amongst a large optimised mesh of series/parr lower wattage resistors.
(making the assumption that 1.5Meg was a maximum value for safety discharge
Then I saw the posters name!.
What the hell. In for a penny, in for a pound ;-)
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