[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [TCML] Measuring secondary current



I got 96V from a simple power calculation (Vpri * Ipri = Vsec * Isec), though that evidently doesn't apply here.

A 1 ohm resistor in the secondary lead is the obvious way, yes, but I wanted to find something that would isolate my 'scope from whatever might be going on (or going wrong) in the secondary. Caution inversely proportional to understanding and all that.


On Mon, 3 Sep 2012, Udo Lenz wrote:

I wonder how you got 96 V for the secondary voltage. The equation for
secondary voltage is

Isec * 2 * Pi * f  * Lsec

Plugging in  500kHz for f, 0.4A for Isec and 13mH for Lsec I get
about 16 kV, which is enough for small sparks.

Secondary currents are low, so you should be able to measure them
by putting e.g. a 1 ohm resistor between the base of your secondary
and ground and measure the voltage across it.

Udo


On Thu, 30 Aug 2012, Jim Lux wrote:
Feeding the ground wire from my secondary through the center of the
newly-minted CT and turning on the coil, I put my oscilloscope probe
across the 14.7k ohm resistor (actually a 10k and 4.7k in series) and
fired up the coil.

The result is a nice 5.6V peak-to-peak sine wave at the ~500kHz resonant
frequency of my secondary...

So 5.6/14.7k = 0.38 mA

110:1 turns ratio implies about 408mA secondary current...

That would be a bit strange, since I'm feeding the primary with 24V @ 2A ... I doubt I would get any arcs at all if there was only 96V at the top of the secondary (and any more voltage would imply the impossible).

There's still the issue that when I calibrated the current transformer against a known voltage/current source I got a very different conversion factor (2mV per mA through the wire under test).



_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla

_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla