# Re: [TCML] Calculating transformer output at lower voltages

```On 6/7/12 6:29 AM, mrapol@xxxxxxxxxxxx wrote:
```
```I know the usual formula Vs/Vp = Ns/Np for calculating transformer
voltages, but I have a problem in that I am dealing with a sealed NST
and don't know the number of secondary or primary turns. What I am
trying to do is calculate the output of a 12kV NST when it's getting
less than 110 volts input. For example, if I feed the NST 30 volts AC,
what does it put out? Is there any way to figure this out without a high
voltage meter (which I don't have) and without knowing the number of
primary or secondary turns?
```
```

```
with no load, and with the voltage LESS than the nameplate input voltage, it scales linearly (the turns ratio isn't changing, after all)
```
12kV out for 120V in
3kV out for 30V in

```
You can also put 120V *in* on the secondary, and measure the primary voltage.. 120V in gives you 1.2V out..
```

```
For larger than nameplate voltages this won't necessarily work: core saturation and breakdown...
```

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