# More: Changing NST Input Freq??

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From:  Andrew Chin [SMTP:chinny-at-ozemail-dot-com.au]
Sent:  Tuesday, June 09, 1998 12:43 PM
To:  'Tesla List'
Subject:  RE: More: Changing NST Input Freq??

I also wonder what would happen if the input frequency was changed from 50/60 Hz to something like 500 Hz?  My understanding of how a transformer works can fill a peanut.  But here's what I can extrapolate from my university textbook.

At low frequencies, the output voltage is low e.g. DC f=0Hz Vout=0.  Also the transformer would get bloody hot as well.  When the frequency is brought up, there is a fairly constant output voltage over a wide frequency range.  Until the frequency reaches a point where the output voltage jumps to a higher peak voltage.  This peaking is due to resonance of the inductive and capacitive elements connected.  After that increase in frequency will decrease Vout.

Well that's my summary of the graph in my book.  I have no idea about how hot the transformer would get, but I suspect that it would be cooler over the constant voltage region.

But increasing the input frequency has one advantage.  That is to reduce the size of the primary cap.  We don't need to design a cap for the 50/60 Hz mains any more.  We can simply use as many turns in the primary as possible, build a cap to resonate with the primary, and then vary the mains frequency to suit the cap.  Any thoughts on this?

With all this in mind, the next problem would be to vary the frequency of the mains.  How would you do that?  I have an idea, which involves a variable duty cycle square wave which closely approximates a sine wave, which is then fed into a H-pack circuit and filtered, but maybe someone already knows a cheaper way of varying the mains frequency.

Andrew Chin	chinny-at-ozemail-dot-com.au

P.S. Forgive me if this message doesn't appear to be formatted correctly.

-----Original Message-----
From:	Tesla List [SMTP:tesla-at-pupman-dot-com]
Sent:	Sunday, 7 June 1998 12:16 AM
To:	'Tesla List'
Subject:	More: Changing NST Input Freq??

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From:  djQuecke [SMTP:djQuecke-at-worldnet.att-dot-net]
Sent:  Saturday, June 06, 1998 7:27 AM
To:  Tesla List
Subject:  More: Changing NST Input Freq??

Well, I misread something on the freq issue but I've been wronger before,
believe me....

Here's probably an ignorant question or two but just so I clarify both sides
of the issue....

What about raising the input freq to NST?

Any idea if a freq divider like I have will double the freq if reversed
wired??

I now figure the NSTs are built to  perform at a given freq and changing
that up or down won't work.  But after seeing how bad things got when you
lowered freq, then raising freq might be better so had to ask.

Thanks,

dj

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