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Re: [TCML] frailty of NSTs


I have some questions about NST failures. I haven't had one yet but was wondering what characterists they have when they do fail. Do they just suddenly stop working or do they become intermittent? Is there a way
to determine NST health after years of operation in a tesla coil?

Thanks for your time.


----- Original Message ----- From: "tesla" <tesla@xxxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Sunday, March 23, 2008 12:22 PM
Subject: Re: [TCML] frailty of NSTs


What is it about NSTs that makes them so fragile? I suspect it is the current through a secondary wound with
inadequate wire size.


These beasts are frail for two main reasons

1) In normal operation the HV is "shorted" by the gas discharge tube when it strikes so that the terminal voltage is at HV for a few fractions of a second. The internal insulation is thus not designed to cope with extended periods of HV

2) They are made with a magnetic shunt which produces large series O/P inductance to limit the current. In Tesla service this inductance can resonate with the Tesla primary cap and this series resonant cct exhibits resonanat rise. This could produce hundreds of kv but naturally the insulation fails prior to that

3) RF from the Tesla may contribute to the failure of the insulation due dielectiric heating I suspect

Ted L in NZ
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