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RE: SIZE of RF chokes?
Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>
Although intuition suggests that running an NST at 140VAC is more
stressful than at 120VAC, I can't think of an actual reason why.
Assuming one is using a static gap, the breakdown voltage and the
voltage seen by the NST is actually NOT a function of the input AC
voltage. Within limits, the breakdown voltage Vgap is strictly a
function of the gap width. Vgap will be essentially the same with 120
and 140 Vin - the difference is that it will fire more frequently
(higher BPS) with a higher Vin.
The RMS current through the NST will be higher at a higher Vin, and
ferroresonance may drastically increase the power throughput, but it's
not clear that this contributes to any NST failure mechanism that I'm
I say crank it to 140V and enjoy!
Regards, Gary Lau
> Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
> Hi JT,
> There are never guarantees with using NST's in TC service. Many if
> not most members in this group run the input of their 120Vac rated
> NSTs at 140Vac. Do what you are comfortable with. If you have a NST
> that is rated at 120Vac_in 12KV_out, then this NST will generate
> 14KV_out with 140Vac_in. Remember, these are rms voltages. If you do
> plan on running your NST at 140Vin, then set your safety gap with
> Gerry R.
> >Original poster: "JT Bowles" <jasotb@xxxxxxxxxxx>
> >So, you're saying i can run my transformer at 140VAC in, and as long
> >as my safety gap is set correctly, I dont have to worry about
> >sweet. Except ,it is a linear relationship right? if i increase my
> >input voltage by 1/6 previous voltage,
> >I should get in increase of 1/6 voltage on the secondary right?
> >That means if i wire my NST for 140VAC in, 14KVAC comes out, correct?
> >>From: "Tesla list" <tesla@xxxxxxxxxx>
> >>To: tesla@xxxxxxxxxx
> >>Subject: Re: SIZE of RF chokes?
> >>Date: Thu, 24 Nov 2005 10:38:59 -0700
> >>Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
> >>Hi JT,
> >>Excessively high voltage is what usually kills NSTs. Use LTR cap
> >>value to avoid resonant charging and a properly set safety gap to
> >>avoid these high voltages. Yes 140Vac will probably shorten the
> >>life of an NST to some extent. If you have a properly set safety
> >>gap and an LTR cap value, you probably shouldn't worry about this
> >>too much as you wont enjoy the hobby as much. I run my 15 KV (21
> >>KVpeak) NST's at 25 KVpeak with a SRSG and haven't lost one yet.
> >>Gerry R.