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Re: [TCML] NST failure ?? variac problem too



The primary should be isolated from the case ground, so it's ka-put. What's  
the resistance across the primary?
 
Tony Greer
 
 
In a message dated 12/3/2008 5:54:14 P.M. Central Standard Time,  
scepp@xxxxxxx writes:

Hello  group,

Well I haven't posted here it a while, but I was testing a new  NST filter 
that I just built with my 12Kv/60mA NST and el cheapo variac  and I popped 
the breaker.  The power switch on the variac was turned  off, it's just a 
switched hot and the dial was set to zero.  I went  to plug in the NST, just 
as I inserted the plug into the variac the lights  in the room dimmed and pop 
goes the breaker  : - 0

It turned  out that the Hot and Neutral was reverse at the AC receptical 
where I  plugged in and the way that my variac is wire, a full 120 VAC to GND 
went  to the NST.  Now I don't think that this should case the breaker to  
pop.  I'm under the assumption that the primary is floating and the  
secondary is supposed to be center tap grounded.  Please correct me  if I'm 
wrong.

I checked the NST with a ohmmeter I I measure 3.3 and  3.7 ohms to ground 
from the 120VAC terminals. ???????
Each secondary  terminal was about 2.5K ohms to ground.   It's an Allanson 
type  455B if that helps.  Is my NST blown??

The variac is one of the  china built white ones, a 2090VR.  This incident 
could have been  dangerous!  I think I have to put a different switch on it 
that opens  the hot and neutral.  Anyone modified one of  these?

thanks,

Shaun Epp 

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