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Re: Transformer Simulation Help Needed

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Matt,

It should have worked fine...

I assume the PFC caps were switched out of the circuit so the NST primaries
were completely open?  

Were you running a coil with this setup?  

Were the ones that died also the ones that were open on the primary?

Maybe the NSTs seeing high frequenices with an open primary is bad...



At 12:32 AM 5/28/2002 -0400, you wrote: 
>Hi All,
>       I recently built an NST farm consisting of five 15/60s and two 15/30s 
>all in parallel.  They were checked to make sure none were connected in 
>opposition. These are all 120v 60HZ units. I made them selectable by putting 
>a switch on each primary, but since I don't have any 15KV contactors, the 
>secondaries were wired in the circuit all the time. After on-off testing 
>over a few days with switchable PFCs and a resistive load (800ohm-at-800Watt), 
>three of the 15/60 transformers had failed (open secondaries). I suspect 
>that the stresses on secondaries in the circuit with some of them idle may 
>have ca! used the problem. I don't know if the idle ones stressed the active 
>ones or vice versa. Then again, maybe it was just their time to die.  
>       Would it be possible for someone skilled in the art of transformer 
>simulation to provide insight before I do any more damage, or unnecessarily 
>tear out all the select switches? What more data would be needed? The 15/60s 
>are all rated 8.23A primary and both 15/30s are rated 3.85A. If this problem 
>is not of general interest, would someone RSVP off-list? 
>Matt D.