Re: What wattage resistors for NST protection?

• To: tesla-at-pupman-dot-com
• Subject: Re: What wattage resistors for NST protection?
• From: "Herwig Roscher" <herwig.roscher-at-gmx.de> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
• Date: Fri, 18 Feb 2000 07:56:00 -0700
• Approved: twftesla-at-uswest-dot-net
• Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

Terry Fritz wrote:

> Those NST filter resistors can see the full voltage on that leg.  
Perhaps 11000 volts peak!  However, the insulation is still adequate.

Terry,

In each HV leg I've used 4 Dale resistors 55W/1kOhm (because 
they were on hand) connected to be 220W/1kOhm. These resistors 
have got an oval shape and an aluminum cooling sheet inside 
which is used for mounting as well.
On powering up the setup for the first time I faced heavy arcing 
from the resistor's winding to the aluminum sheet. I dismantled the 
resistors and cut out 10mm of the sheet in the middle, hoping that 
there is no arcing *inside* of the resistors now. Therefore high 
power resistors with aluminum cases are not a good choice for this 
application as well.

Regards		Herwig

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