Re: Solid State transformer ratio's

On Thu, 25 Apr 1996, Tesla List wrote:
> He first of all states that the RMS impededance is the same
> whether the coil is driven by a square wave, or a sin wave.

Yap. Coil will only draw power at the fundimental frequency if very
high Q coil. (Yes, still an approximation but a very accurate one!)

> He then quotes the imedence turns ratio in a transformer
> as SQROOT(Zp/Zs)=Np/Ns
> Zp, Zs primary, secondary impedance, Np Ns number of turns.
[and so on..]

True if primary inductance makes a high-impedance when considered
in parallel with the reflected secundary load. With eg. air-cored
step-up transformers that may not be the case. In proper design it
should be the case.

> He then assumes a secondary impedance of 500 ohm.
> Which is the DC resistance of the coil.

Probably ac-resistance. I have a coil which has some dc resistance
and much higher ac-resistance. When measured or calculated from the
transmission line theory the ac resistance matches the power draw
at the secundary. (at primary at the turns ratio)

> Builds it, runs it measuring the current through the secondary.
> With a current transformer and an oscilloscope.

That is a good way to find it out. You can also monitor the primary
current in a proper design. You usually have a current transformer
there for current overload limit anyway. You can try first with
low turns ratio and then measure and correct the ratio for a wanted
power draw.

> He found however that the impedance of the coil
> rises greatly when corona is produced and was unstable.

It should rise considering the circuit. That's how it should work.
As the load rises (corona) the Q should go down. That will lower
the voltage and that lowers the power to the corona.
We have phone numbers already, why would we need IP-numbers! -unknown person

Harri.Suomalainen-at-hut.fi - PGP key available by fingering haba-at-alpha.hut.fi