# RE: SIZE of RF chokes?

```Original poster: "JT Bowles" <jasotb@xxxxxxxxxxx>

```
i may, after inserting a new MMC (it is rated double my previous capacitor), crank my power up to 140VAC.
```
```
* I once thought output Hz is equal to the input Hz(i thought my NST has a 60Hz output, always)
```

```
```From: "Tesla list" <tesla@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: RE: SIZE of RF chokes?
Date: Fri, 25 Nov 2005 11:39:33 -0700

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
aware of.

I say crank it to 140V and enjoy!

Regards, Gary Lau
MA, USA

> 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
140Vin.
>
> 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
destroying it?
> >
> >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
```