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Re: [TCML] The Hammertone Predikter
Hi Paul,
I was assuming the CT was a 'pure current source'. I worked some
numbers and your equations work out the same as mine. As Ls goes to
infinity our equations match ;)
But I wanted to check into this...:
http://team-titanium.com/CT-TEST.JPG
I checked the numbers on all the Pearson current monitors I have ( I
have a lot of them too :D ).
The meter is a 100kHz hand held.
Inductance Q ratio Pearson Model
1.156mH 0.15 1:1 2100
6.2uH 0 0.1:1 110
0.3uH 0 0.01:1 101
4.2uH 0 0.1:1 411
0.882mH 0.114 1:1 4100
The numbers don't seem right so either the meter is too weak or the
internal 50 ohm resistance of the monitors is messing everything up.
The Pearson data is here:
http://www.pearsonelectronics.com/current-monitor-products/standard-current-monitor.htm
I also had a Triad CST206-1T like many of use use which is more of a
'pure' CT:
20.10mH Q=29.4 100 turns
The data is here for it:
http://team-titanium.com/TriadChart.jpg
My meter's frequency is probably too low there too... But that chart is
pretty useful!!
No great "results" here at all... But I thought I would mention this
stuff just for the record and in case others wonder why something does
not seem to work right.
It would be interesting to find the time delay during the ring up when
the CT signal is not a pure steady date sine wave:
http://drsstc.com/~terrell/pictures/175ANormalBarePrimary.gif
MicroSim says it is about 4% longer.
The current signal might look something like i(t) = k * t * SIN (w * t)
in that case. My brain seems to have run out of cells on that problem
0:) BTW - My switching delay is about 400nS if anyone cares there. The
drive was turned off at 65uS.
Finn - That is what I meant by the "ring up signal" if it was not clear
before.
Terry
Paul Nicholson wrote:
The lead time at frequency F is given by
Rb = burden resistor ;
Lb = burden inductor ;
Ls = inductance of CT secondary ;
w = 2 * pi * F ;
q1 = w * Lb / Rb ;
q2 = w * Ls / Rb ;
lead = arctan( q1 + 1/q2)/w seconds ;
when Ls >> Lb
--
Paul Nicholson
--
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